Generally the sign out button for Gmail on the web, will appear when you click on your profile picture on the extreme right, what do you do when your avatar or profile pic doesn’t appear? This happened to me yesterday for one of my Google accounts, and to other users in the past, could be a temporary glitch on Google’s side.
What you should do in that situation to sign out of Gmail is to, hover mouse pointer over the right of notification icon, and click on the not-clearly visible circle to see the popup with Google profile picture and sign out button or visiting https://accounts.google.com/ServiceLogin?elo=1 will do.
You should also try the following one by one
- Disabling all labs features if you’ve enabled any to see by using https://mail.google.com/mail/u/0/?labs=0
- Check if this happens in incognito window or private browsing mode in the browser.
- Try Gmail in other browsers.
Note: The issue for me lasted for a short period of time, now I can able to log out of my Gmail as usual without any problems.
Have you faced this?