I have been using OpenAI Discourse almost daily for the last few years. A few days ago logged out to use another Discourse id for some other testing. Switched back to my Discourse Id which worked for other Discourse sites but for OpenAI via oidc fails with the noted reason.
Can someone take a look to see the exact problem.
Please send me a private message if you need the e-mail I am using.
This is not (probably) something any of us can solve, you need to talk to OpenAI if you are having issues with their forum.
If Discourse ID is broken for the community staff can be more helpful by providing logs and coming here if needed but it may be a configuration problem.