I have encountered the same problem with the tunnelbana in Stockholm. Normally I use a card, but on a few occasions I have left it at home or forgotten to top i

I have encountered the same problem with the tunnelbana in Stockholm. Normally I use a card, but on a few occasions I have left it at home or forgotten to top it up, and bought a ticket with the app. When it wasn't scanning and I took my phone off the scanner, I briefly glimpsed the Apple Pay screen before it animated away, so I realised I was "holding it wrong", and was able to get it to scan by holding it at a different angle to keep the NFC sensor at the top of the phone away from reader, but I can imagine a less technically minded user than myself might have serious problems. I don't know anything about the scanner or NFC standards used by this system, sorry.