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

WP-Engine

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!