I don't have any extensions (add-ons) in my browser that interfere with the correct operation of Firefox

Hi

Is this a personal or a corporate (employer or company) Gmail account?

Personal Gmail account

Can we get a screenshot of the issue. It works for me. see screenshot

Did you try Firefox in Troubleshoot Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#search104

Did you clear your browser cache? https://support.mozilla.org/en-US/kb/clear-cookies-and-site-data-firefox

You can check the connection settings and check for possible issues with a Proxy or VPN service.

• Settings -> General -> Network: Connection -> Settings

If you do not need to use a Proxy to connect to internet, select "No Proxy" if "Use the system proxy settings" or one of the others do not work properly.

See also:

• https://support.mozilla.org/en-US/kb/connection-settings-firefox
• https://support.mozilla.org/en-US/kb/websites-dont-load-troubleshoot-and-fix-errors

You can check the connection settings and check for possible issues with a Proxy or VPN service.

• Settings -> General -> Network: Connection -> Settings

If you do not need to use a Proxy to connect to internet, select "No Proxy" if "Use the system proxy settings" or one of the others do not work properly. See also:

• https://support.mozilla.org/en-US/kb/connection-settings-firefox
• https://support.mozilla.org/en-US/kb/websites-dont-load-troubleshoot-and-fix-errors

I don't need a proxy to use the browser, so in the settings I have a check mark in the "No proxy" item.

Can we get a screenshot of the issue. It works for me. see screenshot Did you try Firefox in Troubleshoot Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#search104 Did you clear your browser cache? https://support.mozilla.org/en-US/kb/clear-cookies-and-site-data-firefox

What happens to saved passwords, website settings and other information I have saved in my browser if I enable this feature?

And, yes, I clear the cache in the browser every day.

Can we get a screenshot of the issue. It works for me. see screenshot Did you try Firefox in Troubleshoot Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#search104 Did you clear your browser cache? https://support.mozilla.org/en-US/kb/clear-cookies-and-site-data-firefox

I tried opening Gmail in "Troubleshoot" mode, but it still didn't help to open my mailbox (white screen).

In the "Troubleshoot" section there was a button "Clear Firefox". I didn't click this button, because I think I will lose all my browser settings, as well as my saved passwords. If this is not the case, please let me know.

If Windows Pro version, try testing in Windows Sandbox (VM) to see if you have the same issue. https://www.howtogeek.com/399290/how-to-use-windows-10s-new-sandbox-to-safely-test-apps/

What are your DNS over HTTPS settings? see screenshot What are your DNS settings on your computer and router?

I don't know how, but after more than two months of not being able to open Gmail in Firefox, it just started working by itself.

Thanks to everyone for the advice and willingness to help solve the problem.

Great. Mark it as resolved to get it off of our plate and have a nice day.