Disparity between payment methods in IPhone and on website

Hello, I can use apple pay etc normally in my phone, but when I try to buy something in Arknights it prompts me to login to my apple account and tell me there are no payment methods. Logging into the apple account through website I can’t see the payment methods from my phone either. I could probably just add the same card into the website account, but how does this disparity even exist?