Login fails when Monzo app is locked

The answer seems to lie in the behavior that you’ve described.

That’s a shame, I totally understand your reluctance to switch / adopt another app for this.

It’s worth mentioning that Monzo see protection for the app as a privacy, rather than a security feature & the lock on your phone itself should be sufficient protection. Bearing in mind that in the unlikely scenario that someone steals your phone & bypasses it, Monzo will be liable (bearing in mind their T’s & C’s of course) for fraudulent use of the app.

Lastly, this problem will go away (for most users) once fingerprint protection is added to the Android app.