Just as a heads up, there’s a bug in the Android app at the moment which is preventing people from logging in if their card is blocked. In any recent cases where we might have blocked you card (in the case of suspected fraud on your account for example), you may experience problems logging in. There is a fix on the way in the newest release 
In the meantime please e-mail help@monzo for assistance.
Later releases have come and gone. This issue is now fixed.