We encourage users to add cards to PayPal to spend them at businesses who accept PayPal. In general, it increases acceptance rate.
However, in some cases, PayPal will give an error when attempting to add a card, such as the following:
In almost all cases, that is because the card is being added to a brand-new PayPal account. PayPal, and other businesses, correctly, counterintuitively recognize that a new account is high risk. As an account spends in normal, healthy ways, that risk level decreases.
If you receive that error when adding to your pre-existing PayPal account that has exhibited normal behavior, it is most likely because you are trying to circumvent country restrictions. If neither of those apply, it is likely to be one of the other high-risk behaviors.