This has given me trouble several times, just putting this out there in case anyone else gets that problem.

If you log into the website from EM (or any other page except for forum), you may encounter this:

As shown in the pic, I am logged in but I do not have the permissions to view my posts or messages, nor post/reply to threads.

To fix this, log out and then log back in from forum page.

Also, if you want to log out, then you should first leave forum and do it from EM for example, or you get the opposite bugged state, where you are logged off but can still reply to threads.