My daughter’s Apple Pay suddenly stopped working

My daughter has been using Apple Pay without a problem since we got her an iPhone a year ago. About a week ago it stopped working.

She is having a problem both with an Apple Cash card and with another credit card. They both say "Ready for Apple Pay," and then when she holds the phone near the reader, the card appears. When she double-clicks the side button, nothing happens. This has occurred with several different card reading machines, so it has nothing to do with the machines. 

Not sure what to do, as the problem is not just with a single payment method—it’s happening with her credit card and also with Apple Cash. She has a strong cellular connection in the places she’s trying to use the card.

We do have ScreenTime on her phone, but nothing has changed in those settings and I confirmed that Apple Pay is enabled in Content Restrictions.