Can't call out from app

Hi! I can't make calls out from my app anymore. It stopped working about two weeks ago. There are two of us who use the app on our phones, and the other person's app works fine. I can see and hear the voicemails and answer calls, but can't call out. It starts to ring and then just hangs up. I have deleted and reinstalled the app multiple times, deleted and re-entered my phone number under users, and done everything I can think of. Can you please help? I work from home 3 days a week and this has been a huge problem.