Solved Can't transfer external calls

[Stijn_DC]

Hi all,

I'm have a real head scratcher here.
We've got 4 clients using the same provider, VM, setup, config and in 2 cases even same SIP phone type so I've checked all settings.

One of the customers is complaining that they cannot transfer external calls to a different internal number. But internal calls can be transferred without issues.
When transferring an external call, the called party (external) hears nothing and the internal party keeps hearing the "on hold" music.

• 3CX Version, e.g. Professional Annual 18 u2
• Server OS, Windows 10 21H2
• Is the 3CX Server Hosted and where? On-Premise
• IP Phone Make/Model/Firmware version, e.g. Yealink T46s version 66.86.188.3 (current)
• Provisioning Method: Local
• Trunk Provider or VoIP Gateway Make/Model, Provider supplied SBC/ IAD device connected on a separate subnet
• Has the Firewall Checker passed: YES
• Are custom Phone Templates being used: NO

I've checked the provider template and checked if it's different from the others in any way but it is not.
Checked replace header on both provider template and in extension settings and everything looks the same.
Even more, disabling or enabling makes no difference in this case.

Anything I can check further?
I'm thinking of just scrapping the VM and reinstalling on a Debian based 3CX ISO.

 

[Evolute IT]

Start by updating to U3 and make sure all firmwares and templates are up-to-date.

 

[ChrisC_3CX]

I do also recommend upgrading but also take a look at re-invites in SIP Trunks "Edit >> Options", try disabling both replaces and reinvites and enabling them and check if that makes a difference.

 

[Stijn_DC]

I've upgraded to U3, restarted the modem and SBC, both Re-invite and replaces are turned off by the default template. Should I enable them? This is not required for our other customers.

P.S. for a different reason I also redeployed to Debian

 

[ChrisC_3CX]

I'll PM you shortly for more information on this.

 

[Stijn_DC]

To come back to this case, after many troubleshooting sessions we've isolated this issue to the Gigaset handsets.
When transfering the call from any other phone to Gigaset it would not handle the re-invite properly.
Leaving both calls in a hold state.

The gigaset N870 Pro cluster was running Software version 2.36 or 2.39, we've upgraded this to 2.44 (at this time the latest version) and the issue went away.

 

[ChrisC_3CX]

Thank you for sharing your solution @Stijn_DC! I'm sure this information will prove useful to others facing similar problems!

Glad to see you got this sorted eventually!