TextNow app not working on iPhone 6s

The TextNow app was working fine up till about 2 weeks ago. It suddenly started misbehaving. I’ll write a text, hit send & the text I wrote disappears. I’ll receive a notification of a new text then when I go to the TextNow app the new message isn’t there & I have to uninstall the app & reinstall it for the new message to show up. The app freezes suddenly. I’ll hang up from a call & it’s stuck on in call (can’t use the app cause it’s stuck on that screen) till I restart my phone. I’ll get a missed call notification without my phone even ringing. I’ve uninstalled and reinstalled the app, the internet is working fine that it’s connected to & data is working fine when on that. All other apps work fine.

Does anyone know what to do to fix this? Thanks.