by Jason Caldwell » July 7th, 2010, 4:17 pm
Also, make sure that you've configured your PayPal Pro API Username, Password, and Signature. That general error will occur when there is simply no response at all from the PayPal Pro API. That usually happens when your API Credentials are invalid, or non-existent.
See: s2Member -> PayPal Options -> Account Details
If we did the install for you, please make sure that you disable "Sandbox Mode" after entering your own live account details. Whenever we do a professional installation, we do all testing with a Sandbox account, and s2Member is placed into Sandbox mode during that testing sequence. If you enter your own live account details, but s2Member is still attempting connections to a Sandbox endpoint, this can happen.
See: s2Member -> PayPal Options -> Account Details -> Sanbox Testing