The WebClient in v16 has sound is that correct (I don't mean the Windows App)? If yes, in v18's Desktop App have you ensured that you've selected the correct Speaker and Microphone? Try and select the non-default option and see if that works, as shown below.
What speaker / microphone are you using? Does it work with the Windows Client (as opposed to the Desktop Client)?
Pbx is latest v18 hosted on our servers.
When i say v16 <=> v16 ok , it is between 2 v16 Windows app,
No i have not tested another pbx.
And i ll try firewall testing on client tomorrow