No two way audio between External and Local Extensions

[comversum]

Hello everyone, sorry on my bad English..

I have a strange problem and can not solve at all.

Problem is when Extension - Softphone 3CX iOS App connected via FQDN calling Extension that is in Local LAN - Yealink T42S there is no two way audio and vice versa. External extension can hear internal extension, but Internal Extension can't hear External.
Communication between local LAN extensions is ok, communication between external extension is OK.
Firewall Checker is OK - no issues. Tried PBX Delivers audio without success.

System:

• 3CX Version, Professional Annual 16.0.1078
• Server OS, Debian 9
• 3CX Server Hosted: by me
• IP Phone Make/Model/Firmware: Yealink T42s/66.85.0.5
• Provisioning Method: Local / VPN / STUN / SBC
• Trunk Provider or Gateway Make/Model: Sipgate.de
• Has the Firewall Checker passed: YES
• Are custom Phone Templates being used: NO

 

[Evolute IT]

How is the app connected? Local(Wi-Fi) or External(3G/LTE) ?

 

[comversum]

External (3G/4G), tried public WiFi, home WiFi, no success.

 

[comversum]

How is the app connected? Local(Wi-Fi) or External(3G/LTE)

All external extensions works properly, all internal works properly but two way audio between internal and external not. External extension can hear internal, but internal can’t hear external. Audio between external is ok, audio between internal is ok too.

 

[leejor]

Is this happening with more than one device, placing the call? Is there two way audio when calling the other direction?