Hi –
With the vast changes to PayPal’s API system, we’re struggling to integrate it using the S2Member Pro interface. We’ve entered the API credentials per the “NVP/SOAP API integration (Classic)” option within PayPal, exactly, and keep having this error thrown:
Missing or invalid Username. Please try again.
Any idea what the issue could be?
Hi Shane.
Could you enable logging, reproduce the behavior, and get all the relevant entries from fhe log files? You can post them here, obscuring any sensitive information from them. WP Admin > s2Member > Log Files
Did you verify that all the integration is complete and correct? IPN, PDT, etc.
I look forward to your update. 
For reference, I was able to resolve this issue!
We were using jQuery to auto-generate a username that combined the firstname-lastname and to prevent the user from editing it. Once we modified this to a read-only field, it began working again.
I have no idea why the logs kept telling me that our Paypal credentials were invalid (they weren’t), but I’m guessing that maybe something with the jQuery function was blocking the data from being submitted.
What PayPal API changes are you referring to? Is there something those of us who use PayPal with s2Member Pro need to change? I haven’t noticed any issues.
PayPal still seems to support the SOAP API integration that S2Member requires, but it’s labeled as their “Classic.” I’ve been wondering if that means they’re going to deprecate it eventually.
Their “Developer” section is dramatically different, though, only generating a user secret & key.
Thanks for the reply. Hopefully nothing breaks in the near future (knock on wood).
We were using jQuery to auto-generate a username that combined the firstname-lastname and to prevent the user from editing it. Once we modified this to a read-only field, it began working again.
Thanks for the update! I’m glad you sorted it out.
PayPal still seems to support the SOAP API integration that S2Member requires, but it’s labeled as their “Classic.” I’ve been wondering if that means they’re going to deprecate it eventually.
I haven’t seen any notice mentioning that it’s deprecated. They just came out with a new API later and the previous one they now refer to as the “Classic” one.