I can't pay with a Credit Card-Paypal

I've been using the Print/Ship Option for a couple weeks then it stopped. I can not pay with a CREDIT CARD/DEBIT/ or my Paypal account it keeps telling me It can not accept this form of payment. Customer service does not know the answer they just say my mailing address PROBABLY doesn't match my Credit card info. Nothing. It's still not accepting even AFTER I submit a Report on their website and now I have to drive to the post office, wait in line for hours. And they crazy thing, it accepts my credit card/debit card AT the Post Office, the SAME ONE it's declining on the site. Why won't they give me some time of answer to explain WHY.