This is an fyi for anyone having trouble getting the API credentials accepted in GS (any version). You need API credentials to integrate Paypal so you can keep track of PP fees. I just recently had a three day struggle getting the API signature to work.
I kept getting the error message “security header not valid”. Typically, this error code means a certain code the GS developers put in got switched around and needed to be switched back.
However, that is a very rare occurrence, if it ever happened at all.
I neglected to check the very first thing you need to check when something on a web site suddenly stops working.
These online companies are getting very smart and program the web site to break or crash when a tracker or web blocker is used by the viewer.
This PP problem did not appear to be a broken web site so I completely forgot about the ad blocking I have on all web sites.
As soon as I shut off the ad blocking on Paypal, the credentials were accepted and I finally got back to listing.
Just remember, any web site that suddenly breaks or acts odd or does nothing at all, check you tracking and blocking apps.