You might be out of luck on Mac OS x 10.9 being unable to update beyond 78.15.0 as you will notice that more and more websites no longer support 78 ESR and require a newer version. You can possibly check the Web Console for error messages. *https://firefox-source-docs.mozilla.org/devtools-user/web_console/ Can't you update to a newer OS X version like 10.12 or 10.13 as that would allow to use 115.6.0 ESR ? *https://support.mozilla.org/en-US/kb/firefox-mac-osx-users-esr *https://support.mozilla.org/en-US/kb/firefox-users-macos-1012-1013-1014-moving-to-extended-support