i believe when you tie a card to GPay, the card number is tokenized to another one, the real card number is not presented for payment,
instead a card number tokenized by GPay is presented.
It works for normal payments as they accept any card number as long as it's a valid credit card number.
then the bank end will reconcile with GPay system to match their the tokenized CC number to the actual card tied with that number in GPay system.
For LTA transport app, the card number that is registered with LTA is expected to be presented.
But when you use GPay on the LTA reader, the card number presented by GPay is not the one you registered with LTA.
So maybe the bank needs to work with LTA to match the tokenized number.
https://support.google.com/pay/merch.../6345242?hl=en