Google Pay clearly doesn't realise it's a lockscreen. To enable it, I have to turn off the built in one, which is presumably all Google Pay is checking.
On the phone it calls itself "Android 13 Lock", but on Google Play it's called "Q Lock Screen".
It said something along the lines of "enable screen protection to allow google pay to work". I can't look now as I uninstalled Google Pay in disgust. It didn't work when I tried to pay my vet bill anyway. The shop's machine didn't notice I was waving my phone there. The vet said she has to wave hers all over the place, upside down,. try several times. I'll stick to a debit card. Another lovely invention that's failed miserably - nothing wireless every works. My neighbour is always cursing bluetooth in his work van. Middle of a phonecall, oops, lost signal again.