I'm attempting to access the forum using Internet Explorer (version 11, running under Windows 7 Pro)
I'm logged in, but when I go to forum.arduino.cc I get redirected to https://id.arduino.cc/auth/login/?go=1%26returnurl%3Dhttp%3A%2F%2Fforum.arduino.cc%2F
The page says
You are already logged in. (if you are not automatically redirected in seconds, click here...)
I never get redirected, so I click on the id link. That takes me to my personal info page.
If I then click on the menu, Support > Forum, I get taken back to the "You are already logged in." page