[self-hosted v4.5.13] Add paypal express gateway error

Hi, after key in API username, password and signature, and then click the save button, it redirects to a page with “No Results Found - The page you requested could not be found. Try refining your search, or use the navigation above to locate the post.”
Please advise. Thanks.

I suggest checking for errors in the webserver logs, maybe there’s some sort of security filter blocking it?

Hi Hillel, thanks for your suggestion. I still can’t find any issues. could you please evaluate a bit more? appreciate that.