I was notified by PayPal that the api certificate for a website I maintain was expiring soon. The site is an old oscommerce 2.3.4 site using the PayPal Standard module then available for it. I removed the existing certificate and obtained a new one. I entered the new password into the module. The module, however, requires a signature. A signature is not provided with the certificate. I downloaded the certificate and tried a test live transaction. The transaction was properly processed on PayPal’s end but it returned to the osCommerce confirmation page which displayed an error saying it could not confirm the transaction. The transaction was not shown as paid, but I received a confirmation from PayPal and a receipt from the website. The site accepted and confirmed payments correctly with the old api certificate.
Two questions. What do I do to correct the failure to confirm the payment? What do I do with the downloaded api certificate?
I have searched the PayPal documentation and online extensively, but found nothing on point for either issue.
When using the old classic NVP/SOAP APIs, a PayPal account can have either a signature or a certificate for authentication -- one or the other, never both at once.
If you don't need a certificate for processing in any of your systems, delete/remove the certificate from www.paypal.com/api and generate a signature instead, which is simpler to work with.