ms-client-diagnostics: 22; reason="Call failed to establish due to a media connectivity failure when both endpoints are internal";CallerMediaDebug="audio:ICEWarn=0x12b,LocalSite=
This might be because of internal VLAN restrictions implemented. Because of those rules, Users are not able to contact the VoIP device .
Check there is no restrictions implemented between the user VLAN and the VoIP devices. If that could not be changed, check the MRAS server internal IP address is reachable from both the VoIP device and the user system