It is well known that it doesn’t work at pay at pump petrol pumps yet. You might want to read this thread, Merchants & Banks Who Don’t Yet Recognise the Monzo Current Account Sort Code / Debit Card (open Wiki), to find out where else your card may not work. This is not the current account full release, it is the preview so issues still need to be ironed out. I still have a version 1 of the debit card so I can do even less with mine than you can do with yours. When Monzo issues the final version of the debit card, that should fully work.