PayPal may ask you for credit-card information (even if you have funds in your PayPal account) when you are purchasing a Premium Membership on Chess.com. Fraud protection and issues related to currency are the common reasons for this.
In any case if you have encountered this issue we recommend that you contact Paypal.
Additionally, you may send a payment to the firstname.lastname@example.org address via PayPal and then contact Chess.com Support to let us know your payment has been sent. We will add your premium membership to your Chess.com account.