Show the issue. Let me see what happens when I log into my yahoo account.

Went to yahoo.com, clicked on email icon, signed in and it works. see screenshot Does it happen with Firefox in Safe 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 also clear all items for a single site. https://support.mozilla.org/en-US/kb/remove-websites-address-bar-suggestions