Okay here's what I've done.
Backed up the configuration.
Uninstalled the 3CX server application.
Rebooted the server.
Run the 3CX sysem cleaner utility and completed the necessary action (step 3 delete 3 CX) folder.
Installed the latest version.
Restored the configuration.
3CX server has started okay.
All of the 20 extensions fail to register with the server.
The VoIP line still makes no attempt to register with the provider.
The situation has worsened by following the suggestion to update to the latest version. Now the internal system isn't working.
Here's the text from the 3CXPhoneSystem Log file
12:34:21.984|.\CallMgr.cpp(1061)|Log2||LoadLicenceInfo:[CM501010]: License Info: Load Failed<br>
12:34:22.265|.\SLServer.cpp(870)|Error1||??:Unknown system [DBProvider] tries to connect!<br>
12:34:26.953|.\CallMgr.cpp(147)|Log2|CallManager|CallMgr::Initialize:[CM501001]: Start 3CX PhoneSystem Call Manager<br>
12:34:26.953|.\CallMgr.cpp(148)|Log2|CallManager|CallMgr::Initialize:[CM501002]: Version: 7.0.4708.0<br>
12:34:27.546|.\CallCtrl.cpp(21)|Log2||CallCtrl::thread:[CM501007]: *** Started Calls Controller thread ***<br>
12:34:27.656|.\CallMgr.cpp(729)|Log2|CallManager|CallMgr::findLocalIPs:[CM501006]: Default Local IP address: [172.16.160.7]<br>
12:34:36.968|.\CallMgr.cpp(853)|Log2|CallManager|CallMgr:

nAddIPs:IP(s) added:[172.16.160.7]<br>
12:34:37.515|.\MSInterface.cpp(734)|Log2||MediaServerConnected:[CM112000] Media Server is connected<br>
12:34:45.609|.\Extension.cpp(310)|Log2||ExtnCfg::updateContact:[CM504001]: Ext.*0: new contact is registered. Contact(s): [sip:*
[email protected]:40000;rinstance=c2d88cecc80cefc9/*0]<br>
12:34:45.750|.\Extension.cpp(310)|Log2||ExtnCfg::updateContact:[CM504001]: Ext.*1: new contact is registered. Contact(s): [sip:*
[email protected]:40000;rinstance=3d2d0e15e49531b4/*1]<br>
12:34:47.734|.\Extension.cpp(310)|Log2||ExtnCfg::updateContact:[CM504001]: Ext.999: new contact is registered. Contact(s): [sip:
[email protected]:40600;rinstance=5bd9145f1257c8a9/999]<br>
12:35:00.500|.\VExtMgr.cpp(78)|Log2|DataBase|FaxCfg::updateContact:[CM504008]: Fax Service: registered as sip:
[email protected]:5060 with contact sip:
[email protected]:5100;user=phone<br>
12:35:06.437|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-bb9cc6a8 cseq=REGISTER
[email protected]:5060 / 15010 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:09.453|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-3e08e504 cseq=REGISTER
[email protected]:5060 / 61549 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:09.906|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-5e12123e cseq=REGISTER
[email protected]:5060 / 52870 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:10.890|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-6a5517b9 cseq=REGISTER
[email protected]:5060 / 60293 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:11.625|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-2b635047 cseq=REGISTER
[email protected]:5060 / 57635 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:13.609|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-c0083269 cseq=REGISTER
[email protected]:5060 / 39646 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:14.062|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-3794b18f cseq=REGISTER
[email protected]:5060 / 49104 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:14.937|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-c12068d8 cseq=REGISTER
[email protected]:5060 / 8142 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:20.015|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-4c1d3066 cseq=REGISTER
[email protected]:5060 / 9844 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:20.203|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-17a76887 cseq=REGISTER
[email protected]:5060 / 41113 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:22.281|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-2e60e2a4 cseq=REGISTER
[email protected]:5060 / 41832 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:26.984|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-6688dbf0 cseq=REGISTER
[email protected]:5060 / 53682 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:27.234|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-4e2a9606 cseq=REGISTER
[email protected]:5060 / 7937 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:27.765|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-8d939d62 cseq=REGISTER
[email protected]:5060 / 20416 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:28.843|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-e03a5554 cseq=REGISTER
[email protected]:5060 / 29592 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:28.859|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-37337e2 cseq=REGISTER
[email protected]:5060 / 10664 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:35:32.656|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-fa96395b cseq=REGISTER
[email protected]:5060 / 20608 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:39:59.609|.\VExtMgr.cpp(78)|Log2|DataBase|FaxCfg::updateContact:[CM504008]: Fax Service: registered as sip:
[email protected]:5060 with contact sip:
[email protected]:5100;user=phone<br>
12:44:59.734|.\VExtMgr.cpp(78)|Log2|DataBase|FaxCfg::updateContact:[CM504008]: Fax Service: registered as sip:
[email protected]:5060 with contact sip:
[email protected]:5100;user=phone<br>
12:49:59.843|.\VExtMgr.cpp(78)|Log2|DataBase|FaxCfg::updateContact:[CM504008]: Fax Service: registered as sip:
[email protected]:5060 with contact sip:
[email protected]:5100;user=phone<br>
12:54:59.937|.\VExtMgr.cpp(78)|Log2|DataBase|FaxCfg::updateContact:[CM504008]: Fax Service: registered as sip:
[email protected]:5060 with contact sip:
[email protected]:5100;user=phone<br>
12:55:06.703|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-5dd491ee cseq=REGISTER
[email protected]:5060 / 15012 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:09.703|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-d5c2db5b cseq=REGISTER
[email protected]:5060 / 61551 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:10.156|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-d5d77e8d cseq=REGISTER
[email protected]:5060 / 52872 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:11.109|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-895f3552 cseq=REGISTER
[email protected]:5060 / 60295 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:11.843|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-aba95ff0 cseq=REGISTER
[email protected]:5060 / 57637 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:13.859|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-783b53ee cseq=REGISTER
[email protected]:5060 / 39648 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:14.312|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-c3c6b94f cseq=REGISTER
[email protected]:5060 / 49106 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:15.203|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-7a50eab1 cseq=REGISTER
[email protected]:5060 / 8144 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:20.171|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-65f10bb cseq=REGISTER
[email protected]:5060 / 9846 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:20.500|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-25603d9a cseq=REGISTER
[email protected]:5060 / 41115 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:22.562|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-a138f28b cseq=REGISTER
[email protected]:5060 / 41834 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:27.171|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-5ff4c589 cseq=REGISTER
[email protected]:5060 / 53684 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:27.515|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-e4649ccf cseq=REGISTER
[email protected]:5060 / 7939 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:28.046|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-a26c1f1c cseq=REGISTER
[email protected]:5060 / 20418 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:29.000|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-b0096d2a cseq=REGISTER
[email protected]:5060 / 29594 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:29.031|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-8ee35173 cseq=REGISTER
[email protected]:5060 / 10666 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>
12:55:32.984|.\Authorization.cpp(103)|Critical0|Authorization|AuthMgr:

nAuthFailure:[CM102001]: Authentication failed for SipReq: REGISTER 172.16.160.7 tid=-eedbe51a cseq=REGISTER
[email protected]:5060 / 20610 from(wire); Reason: Credentials don't match, check that authorization-ID and password match the ones in extension settings<br>