This might not be news to some but it was for me. In the US now and tried to pay with Android Pay on my Nexus 6 which has a stock ROM but the bootloader is unlocked (I know I did this but not sure why). I am using a US credit card so it's mot an issuing bank issue.
The terminal popped up a message saying
“Android pay can’t be used on this device… Google isnt able to confirm that your device or the software on it is is Android compatible. You many need to unroot your device.”
I think this is a recent update to Android 7 slipstreamed out to some releases (I only recently got the Anroid 7 update).
That's annoying since I had used Google Wallet with no problem but appaently Android Pay keeps a tokenised version of your card on the phone which it uses to send to the terminal so more security is required. i suspect PCI-DSS would be an issue.
I could relock the bootloader to check but I have no PC with me on this trip and it could wipe the phone which would be a hassle.