I have been having a repeated issue for a couple of months now, around once a week (sometimes more often). My app won’t refresh, even though I am getting notifications about payments, etc. I occasionally get an “access token is expired” message if I try and categorise a previous transaction.
Only way to refresh the app is to delete it and reinstall every time, which is becoming a real chore. All google searches have suggested this, but I can’t keep doing it every time!
This sounds like a keychain bug. Keychain is a piece of software that is part of iOS, which the app uses securely store your credentials. Unfortunately these bugs are really hard to track down and fix
Could you report this in chat? Something you can try in the interim is going to the settings app, scroll down till you find Monzo, tap Monzo and then turn on the little “Reset Session” option. Finally open app again, give it a moment, force close it and reopen.
With a bit of luck that might get Keychain to start behaving again.