If you see the following error on PayPal's checkout site after proceeding from your E-junkie Cart or Buy Now buttons to checkout with PayPal:
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, firstname.lastname@example.org and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
That error can happen if the PayPal Email address you have entered in your E-junkie Seller Admin > Edit Profile screen does not match up to any existing account at PayPal's end. Double-check the PayPal Email you have entered there for any typos, and note that must be either the email address you use to log into PayPal or a Confirmed secondary email you have added to your PayPal account.