We'll definitely need more info on the issue if we're to narrow it down:
• So is every single mobile client unable to make calls, both Android and iOS? YES
• Are all mobile clients having the issue regardless of where they are connected, different Wifi network or LTE? YES
• In your initial description you mention not being able to make calls, does that mean they are able to receive calls? NO THEY CANT NEITHER CAN THEY INITIATE A CALL
• Do you get a specific error on the mobile app when you try to make a call? NO, I JUST CANT DO ANYHTING ON THE APP
• Does presence information work in the mobile apps(can see extensions in status, can see contacts, etc)? YES, BUT CANT CALL ANY OF THE CONTACTS\EXTENSIONS.
• Where is the PBX hosted and on what OS, are the mobile clients local or remote to it? WINDOWS SERVER 2019 AND WINDOWS 10 PRO 64 BIT