GPay and TWRP: NFC payment not possible / forbidden

After flashing my old Samsung smartphone to TWRP (s. this posting) and before installing a custom OS, i did some tests with the original Android OS.
Everything worked but GPay refuses to work:

Your Phone can't make contactless payments
Check your phone software to see if it meets standards
Check software"

and the button "Check software" opens this popup:

Your phone doesn't meet software standards

You can't make contactless payments with this device. It may be rooted or running uncertified software. Contact your device manufacturer or visit Google Pay Help for more info.You can still use Google Pay to pay online.

OK

So GPay does not only check the OS - it checks the bootloader, too.
Even if you did not rooting/jailbreaking your OS...