I just got a new phone this month (Pixel 3a XL). Several times a day when I open the Series Guide app, I see a message at the bottom telling me to sign in. Is it a coincidence that this is happening a lot since I got the phone, or was this something added in the latest update that automatically logs you out after exiting?
Welcome! Sounds like SeriesGuide Cloud. Make sure to install the latest software update for your phone and that Google Play Services are up-to-date.
If that won’t work, you can help me figure out the issue by sending debug logs: enable debug mode in settings, restart the app. Then after you are signed out again, from the main menu (top left) tap Debug view, then Show logs and Share logs and email them to uwe AT seriesgui.de.