This issue could be caused by a browser cache or cookie problem in Firefox. Here are some steps you can try to resolve the issue: Clear the browser cache: In Firefox, go to the menu button (three horizontal lines) in the upper-right corner, select "Options," and then click on "Privacy & Security." Under the "Cookies and Site Data" section, click on "Clear Data" and then select "Cached Web Content." Disable browser extensions: Sometimes, browser extensions can interfere with the normal functioning of websites. Try disabling any extensions you have installed in Firefox and see if that resolves the issue. To do this, go to the menu button, select "Add-ons," and then click on "Extensions." From here, you can disable or remove any extensions you don't need. Disable tracking protection: Firefox's tracking protection feature can sometimes interfere with websites, including Yahoo Mail. To disable it, go to the menu button, select "Options," and then click on "Privacy & Security." Under the "Enhanced Tracking Protection" section, select "Standard" or "Custom" and then toggle the switch to the "off" position. Clear Yahoo Mail cookies: In Firefox, go to the menu button, select "Options," and then click on "Privacy & Security." Under the "Cookies and Site Data" section, click on "Manage Data" and then search for "yahoo.com" in the list of stored cookies. Remove any Yahoo Mail cookies you find, then close and reopen Firefox. If none of these steps resolve the issue, you may need to contact Yahoo Mail support for further assistance.