What OS? What version of Firefox? I don't use it, but I'm able to sign into my gmail account with Firefox. see screenshot Do you have the same issue with Firefox in Troubleshoot Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#w_how-to-start-firefox-in-4troubleshoot-modesf5safe-modesf Did you try clearing the browser cache? https://support.mozilla.org/en-US/kb/how-clear-firefox-cache# You can try to clear all items for a single site. https://support.mozilla.org/en-US/kb/remove-websites-address-bar-suggestions Last step if needed, you can refresh Firefox. https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings