Hi,
I really like this plugin and have been looking and testing multiple solutions.
I found that if I try to log in to subsite.mainsite.com/wp-login.php, using Google, I get the follwing error
Session mismatch - try again, but there could be a problem setting cookies
It then redirects me to the mainsite.com/wp-login page.php and if I try again it works but that brings me back to the main site, not the subsite I was trying to log in to originally.