Error #10002. Security error. Security header is not valid

Getting this error when I try to make a payment to upgrade from a free membership to paid through the PayPal gateway as a test client on my site.

https://www.inwbands.com/membership/upgrade-from-free-membership-to-part-membership/

Any suggestions?

Could it be the email I signed up with does not have a PayPal account associated with it? Or shouldn’t the form be asking for the PayPal login information?

Same error for first time sign ups too. Ugh I’d really like this to work. Never anticipated so many errors and customer service replies that takes days!

If PayPal is working as it should, and you’re using live transactions, that error means that either you have not put the right credentials in somewhere, or you have entered the wrong endpoint.

But you’ll have noticed my qualification about PayPal. It’s notoriously problematic. (Not just with s2Member, but for everyone.)

You’d almost certainly make life much simpler for yourself if you used Stripe instead.

Thank you for the reply. I’ll look into Stripe tomorrow.

Actually, although I already had API Credentials, they did not contain the signature. I deleted the Credentials and added the Signature instead. Works now.