Occasionally, customers have reported receiving the following error when trying to signup, "Invoice has already been paid” (or similar). This PayPal error message is very misleading. We found that this message appears because the PayPal Account had an expired/invalid Credit Card set as the “primary" payment method.

To resolve this, add a new valid credit card to the account and designate it as the "primary" payment account in PayPal. The message should no longer appear and you should be able to complete your purchase.