A rare-interesting UX problem with people thinking the screen froze. I guess it’s easily solved, but there are surely many ways to solve it.
For instance the Stripe Terminal reader is immediately to the right of the iPad POS, but a good number of people don't know where to tap the card. I need to design an arrow on the checkout screen for that because I've seen many people tapping the card to the iPad screen. I think Square got them used to that.