Firefox does not load-multiple copies prevent
Firefox does not load it says another Firefox is open and must close - or, it does not load at all, only a tab. I have taken this to the Geek Squad and they couldnt figure it out either even after reloading the browser. nancy
Opaite Mbohovái (1)
Step one would be a reboot.
Make sure you close the browser using;
Windows: Menu > File > Exit
Mac: Menu > Firefox > Quit Firefox
Linux: Menu > File > Quit
Some users have reported issues when closing the browser using the X upper-right of the window.
https://support.mozilla.org/en-US/kb/firefox-already-running-not-responding
https://www.basezap.com/cant-open-firefox-because-a-copy-of-firefox-is-already-open-mac/