I’ve got the same thing with my starling account . Won’t let me add the card back to my Apple Pay after resetting my phone the other week.
The mobile wallet toggle under card controls won’t let me turn it on.
Added my Tesco credit card and NatWest bank account no problems to it
Bit of a shambles really that a mobile digital bank cannot let you add a card to Apple Pay and don’t seem to give you a valid reason for it . Was on the hunt for a new joint account seeing as our NatWest one is changing the rewards account and was looking at moving our joint account to starling but this has put me off doing that .