I see. This sounds like an issue for PayPoint to fix, as they’re the developer of that app rather than OVO.
The other snag I can see here is that you’re running a pretty old device at this point, for which Android 8.0 Oreo is the last available Android release it can get - the most recent is Android 14 with Android 15 coming in a few months from now. That’s quite a lag which may suggest that you’re right on the edge of what the app will support.
I’d say you’ve got at most two years left before the OVO Top-Up app - and most of your other apps - totally lock you out on that device.