Recently, I started experiencing this issue on Chromium under Linux Mint 20.
Every time I opened Chromium and tried to use a Google service, I would not be logged on them. For example, opening Gmail would show me the login page. I, then, proceeded to login, and everything worked fine until I closed the browser. Opening Chromium again would bring me back to the same problem: I was signed out from Google and prompted to login.
This only happened to Google, other websites worked fine.
Clearing the cache, trying different password stores and even deleting every Chromium file on my home directory and starting clean didn’t solve it.
What did the trick is the following:
- On Chromium, go to settings.
- Click on “Sync and Google services”.
- Uncheck “Allow Chromium sign-in”.
- Restart the browser.
This issue seems related to the recent announcements around the Google Sync API and “ 3rd party browsers ”. Note that if you try to login to Google through the browser menu it fails silently.