Dear Eddv123
about your Questions
Is this over 3/4G connection? Or WiFi? 3/4G and wifi same ( work in internal network )
Is the connection stable? YES
Does the logging on 3CX give any indication as to what the issue might be? message is ( Provisiong error )
Are you running the latest supported soft clents for the version of 3CX that you have? Yes last soft