I have issues occasionally where an app will not work either at all (dumps off as soon as I touch it) or does whacky things that it should not, like gives odd error messages, or does not load up, or loads and immediately closes, or no log in works, etc.
It could be a number of things interfering with the app:
Your Internet may not be strong enough to run it or you need to restart your router - I had trouble with a handful of apps in the mountains, but a couple worked. I checked the Internet connection, and it said I was logged in. After about ½ hour, the other apps began working. It might have been spotty coverage and not enough signal for some apps.
The Internet connection might be set up on the wrong Internet account by a default. Check that it is the correct one.
You might be using it in a “dead zone” where the Internet is not picking up.
The app could be outdated, and it needs you to check if there are updates to it.
It might no longer be supported, and its functionality is gone.
Your phone might need to be restarted to clear out old muck and let it load up again.
The password may need to be updated as it might be expired, no longer complies with requirements.
The app might need to be deleted and reloaded.
Try the different fixes and you might get it working again, unless the app or its connection is bad – then you just have to try again later. PR