FWIW, I was having the same issue here and went through many of the above suggestions. I have 3 different Gmail tabs open and pinned in my main window. Two of the 3 are domains, not @gmail.com and only the @gmail.com account/tab was working properly. I closed the pinned tab, opened a new tab, went to the mail.domain.com and was able to log in to the standard version. I then repinned the tab and so far, everything is working fine.
So, at least in my case, closing the pinned tab for both of those hosted gmail accounts fixed the issue. Hopefully this helps others.
I had the same problem just now. After reading and trying a few suggestions in this thread, this is what worked for me.
Ok, it didn’t work for me either until I “unregistered” every service worker for the site.
Steps to unregister service workers:
Open the devtools as mentioned in many posts above
Go to the “Applications” Tab
Select Service Worker
You should see a list of service workers with blue links to View Network requests, Update and Unregister. — Click “Unregister”
Follow this step for any and all mail.google.com service workers (this is if you have multiple gmail accounts)
Do refresh didn’t immediately work for me, but it did work once I typed mail.google.com in the address bar.
PS: Service workers are magical scripts that help webapps perform more like native apps. They enable some really strong browser caching mechanisms, and I suspect the Service Workers didn’t sync propertly in a recent update.
Thanks for the write up. I couldn’t find any service workers for gmail, I removed any Youtube ones i could find (no other google ones). Then I reset all of the above, cache etc. Google in general is not logging in, so maybe a more specific problem with the accounts page? Access to account via Youtube didnt work, hangs. Thanks again.
I had the same issue for a few days and today I had the idea to change the User Agent, just in case Gmail doesn’t accept Brave anymore… Guess what ? It worked…
I use now a Chrome 90 / Win10 UA thanks to User-Agent Switcher and Manager extension.
It might have worked for that user in particular, but it’s far from the solution to this weird issue. I’ve asked users to clear absolutely everything (which as you understand includes logging out Gmail) and it wouldn’t work.