@Hossein, thanks for the quick response!
Found a workaround to the log out problem but it's very awkward.
Instead of attempting to log out from App Inventor, go to Google.com and log out there. THEN, clear your recent browsing history. Then go back to
ai2.appinventor.mit.edu and you can log into a different google account for App inventor.
Any thoughts on the AI2 Companion no longer functioning? Is it possible these two issues are related? They popped up at the same time but that could be coincidental. I de-installed the companion app on my Android phone and then re-installed it.... no difference. Currently running version 4.2 of the companion app.