Decline loop

I’ve had a delayed payment declined- even though I added money to the account it seems trapped in a multiple decline loop- any suggestions on how to fix

What payment? Card payment? From a Pot?

Apple Pay card payment- thanks

It is wallet not fetching data again. Even if you are not paying for anything, double tap the power button to bring up the cards then select the Monzo card and just wait few seconds.
If you enabled Wallet to show you balances for Monzo you can manually refresh it in the wallet app.
I once had it with another bank but it was an Apple issue