Wallet showing "card unavailable" on one device only

Since updating iPad to iPadOS 13.3 this week, one of the three credit cards that were previously in my wallet has disappeared and the other two (including the Apple Card) are showing "Unavailable".

On my other two devices (Macbook Pro and iPhone), all three cards show up normally, as before.

The update has affected only the iPad. What is also strange is that Wallet is supposed to sync between devices, so the sync is obviously broken too.

(To anticipate likely replies: yes, I am signed on with the same Apple ID; yes, I have tried re-starting the ipad; I have tried deleting and re-adding the card: initially, the card shows correctly but after several minutes it goes back to "unavailable".)