Welcome to the community and thank you for your post.
I do understand your concern. It sounds like the card you have added may not be eligible for the transaction you are trying to make.
I would suggest you check if you have confirmed your card. If not, this could be causing this issue. To confirm your card, simply follow the steps here. Once you have done this, please try making your payment again.
I have had a PayPal account for more than ten years and have used the linked credit card 10 times this year including 4 times this week. It is for this reason I ask why when trying to purchase something with this one vendor I was being asked to enter a card number. I could have just followed the prompt by entering my card number regardless of the fact that I already have a card linked to my PayPal account. I didn't to that, obviously, because I'm concerned that there might be a glitch allowing my credit card number to be revealed to someone I don't know.
