Google pay arrives on debit cards

Google rebranded their Android pay to Google pay and some Taiwanese bank included service to their debit card
As foreigners here are hard to get credit card this seems good option if you want pay things with your cellphone. I have Cathy United Visa debit card and it worked in Starbucks but Family mart and 7/11 rejected me even they advertise support for it. My Chinese is below basic level so I couldn’t figure if they done something wrong or they just don’t accept that particular debit card…

Already got Line Pay on my debt card. If I register that card to the google pay, do I get points on both? XD

Has anyone successfully used Google Pay at Family Mart? The app advertises it as working at Family Mart, but my first attempt at paying was rejected because i had the “wrong credit card”

I though Google Pay was meant to be card-agnostic (it creates a virtual “Google pay” visa card), any idea what went wrong?