I used same credit card, resetting phone is helpless to this issues. I uninstalled Google Pay and reinstalled it again, those cards attached to the apps previously, automatically appeared when the app is installed. No need to key in one by one.
Very likely is the update that kills the G pay. I feedback to xiaomi service centre, but nothing they could help me on this. But i told them this problem, also told them not only me having problem like this, other users experienced more or less the similar set of issues. Hope they will come out some patch firmware to fix this. They replied, have to wait for the patch to be developed though.
No choice, just wait then....hahaha.....
Half way there, but still unable to use on MRT....sad.....