kap In any case I am under the impression the Bunq mastercard is under Netherland number allocation therefore you will NOT be able to add it in Austrian Google-pay.
bunq has different number ranges for pretty much every EEA country, even for customers from Iceland. So that shouldn't be the problem. Or rather, it's probably actually the reason for you not being able to use Google Pay with your cards. Because bunq doesn't support Google Pay in Austria, and therefore Austrian bunq cards don't work. If you actually had Dutch bunq cards, pretty sure Google wouldn't mind if you added them to your wallet.