How to troubleshoot Facebook: SDK returned an error
The "UM Social login - Facebook: SDK returned an error" Facebook login error is usually caused by aggressive server page caching but it can be easily resolved by requesting to set up a special cache exception for Ultimate member pages.
These pages should be excluded:
/login /register /account/social
Social login on WP-Engine requires special cache exception for the Ultimate member pages.
To do this, simply submit a support ticket to WP Engine via their support portal and ask them to exclude Ultimate member pages from the cache.
Feel free to copy and paste this sample ticket:
Hi, My site runs Ultimate member plugin and we are having some issues with page caching and social login. The Ultimate member team has instructed us to ask you to place a cache exception on the following pages: add your site URL /login add your site URL /register add your site URL /account/social Could you please add the following URLs to the exception list? Thanks!