Downgraded now it's borked

I downgraded from Metal to Black.

Google Pay works, the card works on tap and pay but all my subscriptions are failing, I can't buy online using the card details.

Support can only tell me I'm keying my expiry date in wrong as that's what it shows their end.

I'm not! All these details worked until I downgraded. Now they don't.

Anyone else got this issue?!