incoming calls on phone app

incoming calls are not ringing to the mobile app. They ring on the desktop, but not the cell phone. when I open the mobile phone app there is a message displayed briefly saying there is no network connection. I cannot switch from the desktop to mobile app, it errors out. I know my network connection is good. all other apps are able to operate. I am on Wi-Fi due to the lack of cell signal in our building. this still happens when on mobile data. 

After the mobile app opens and the connection error message goes away, I can instantly make calls out.