I also have the same exact issue, I got my card a month ago. I tried with my family member's airtel thanks app and it worked there.Hi, recently got my airtel axis mastercard credit card.
I have tried paying my bill multiple times with this cc on the thanks app. But it's failing every time. My cc is working. I have made a transaction on Swiggy, and works fine.
In Airtel app, it won't let me go to the payment gateway.