Hi
thanks very much for your reply.
I have just come across the following article and not sure if this is supposed to solve this same issue? Does this make any sense to you?
Synchronize state from website to Discourse.
Login
When a user is logged in on the website, the URL that link to the forum site should be set to fourm.example.com/session/sso . Then when a user click this URL to visit forum, he will be logged in to Discourse automatically.
If your site allows anonymous browsing, make sure you detect the user login state and only append the /session/sso part for logged in user. For anonymouse user just direct them to forum.example.com/
Without this setup, when a user navigates to Discourse, he will need to click the Discourse login button to login.