Thanks Simon, yes the user is logged into WordPress.
The odd in my scenario is that I have one main WP site (WPSite1) that is the DiscourseConnect Provider for Discourse using WP Discourse,
Then I have a second WP Site (WPSite2) that synchronizes user database with WPSite1 using WP Remote User Synch plugin
I don’t know why it would interfere with the expected behavior you mentioned though, because when I login in on WPSite2, and then navigate to WPSite1, I am already logged in on WPSite1 as well.
But what is happening is that even after logging in on WPSite1, which is the DiscourseConnect Provider, and I click on a URL like https://discourse.example.com/session/sso?return_path=/g/private_group, it takes me to the SSO WP Login form.