Steam Market card verification doesn't work with Monzo

Issue:
I added money via Monzo to my Steam Wallet in order to make a purchase on the Steam marketplace, Steam wants me to verify my card in order to use that money on the Steam Market, they have a page which requires / allows you to request the card verification process but it fails every time, the App doesn’t show the declined payment tests at all, the web version does.

It makes it so I put money into my Steam account, but because I can’t verify I effectively can’t use it.

Details to reproduce:
OS: IOS
Device: iOS 26.3.1
App Version: 7.21.0 #7210051

Screenshots:

This is a Steam issue, not Monzo.

Have a search, it’s been reported before.