I think I know what can be, but let’s see if it’s what I think. It’s been happening in a similar way in the DevSupport Forum immediately after the Xbox Live authentication migration. Try deleting all cookies and site settings, including the MSFS forums and Microsoft login, etc. Then, sign in on either the General sim forums or here the DevSupport forums using the Microsoft account credentials, and reply ‘No’ when prompted to ‘Stay signed in’. Try accessing on the other site immediately after (i.e., first General forums, then DevSupport or vice versa). It’s probable that keeping the cookie session has something to do with the issue.
It’s kinda weird anyway.
I look forward to what happened.
Regards,
Carlos Gonzalez
CEO & Lead Developer - NextGen Simulations