Receive "480 Temporarily not available" when calling Ring Group, on occasion

[Dynamic Networks]

3CX Version 16.0.641

Client has a ring group with all extensions in it. To be clear, they have half as many people in the building as they do physical extensions.
All calls forward to this ring group. All phones ring. After 25 seconds, it goes to the voicemail of a specific extension. Simple enough.

On rare occasions (a couple of times a day), when a call comes in, the call will hit the ring group, then IMMEDIATELY show in the call log "Not Answered", then dump the caller into voicemail. Won't ring the phones or anything.

Again, keep in mind that there are more phones than people, more concurrent calls licenses than people, and more people than trunks, so the ring group is not technologically or physically possible to be completely busy. They would run out of any number of other resources first (trunks, then people, then concurrent licenses, in that order).

Call Log shows:
09/21/2020 2:29:48 PM Cell Phone OH:G1 (AAAEEENNNN) Ext.002 () 00:00:00
09/21/2020 2:29:48 PM Cell Phone OH:G1 (AAAEEENNNN) RG Weekday Ring All (800) Not Answered
09/21/2020 2:29:49 PM Cell Phone OH:G1 (AAAEEENNNN) VMail (100) 00:00:08

(Extension 002 above is a Call Flow Route.)

The Activity log shows:
T:RingAll:800@[Dev:sip:[email protected].204:5060,Dev:sip:[email protected].217:5060,Dev:sip:[email protected].226:5060,Dev:sip:[email protected].191:5060,Dev:sip:[email protected].187:5060,Dev:sip:[email protected].224:5060,Dev:sip:[email protected].231:5060,Dev:sip:[email protected].232:5060,Dev:sip:[email protected].232:5060,Dev:sip:[email protected].232:5060,Dev:sip:[email protected].232:5060,Dev:sip:[email protected].212:5060,Dev:sip:[email protected].232:5060,Dev:sip:[email protected].232:5060,Dev:sip:[email protected].232:5060] from L:1801.1[Line:10002<<AAAEEENNNN] failed, cause: Cause: 480 Temporarily not available/INVITE from x.x.x.232:5060

So: all the phones were simultaneously not available, while employees were sitting in the office and available at the time?

Thoughts?

 

[cobaltit]

https://www.3cx.com/community/threads/information-to-provide-when-requesting-help.67558/

Without knowing your setup, I would say that maybe there was a temporary issue affecting the ability to see the phones.

 

[Dynamic Networks]

• 3CX Version, Professional Annual 16.0.641
• Server OS, Windows 10 Professional, firewall disabled
• 3CX Server: On the client's network.
• IP Phone Make/Model/Firmware: Yealink T27 (the 100 extensions), Yealink W56H through W60B Base (the 200 extensions) - all firmware up to date to 3CX requirements as of time of posting.
• Provisioning Method: Local
• Trunk Provider or Gateway Make/Model:
  • Incoming Calls: Grandstream GXW4104
  • Outgoing Calls: Wiretap Telecom
• Has the Firewall Checker passed: Yes
• Are custom Phone Templates being used: No
• Network Switch: Gigabit Ethernet on HPE 1820-48G-PPoE+ (370W) Switch