We have a Google Cloud hosted version of 3CX up and running and the Windows/iPhone/Android phones are working perfectly. We are attempting to connect a Yealink T23g phone, the phone provisions, shows presence information and rings when dialed but when you answer the phone the caller carries on hearing ringing and there is no speech. Extension on the 3CX server is using 5065 for SIP and 14000-14009 for RTP. Disallow use of extension outside of LAN is unticked. PBX delivers audio is ticked. Remote fire wall: Netgear N150 Port 5065 TCP/UDP forwarded to static IP of phone in and out. Ports 14000 to 14009 UDP forwarded to static IP of phone in and out. SIP ALG disabled. NAT enabled. Firmware on phone is 220.127.116.11 What have I missed?