You appear to be using the old eol macOS 10.10. https://support.mozilla.org/en-US/kb/firefox-mac-osx-users-esr For macOS 10.9, 10.10, 10.11 the most current version of Firefox you can run is Firefox 78.15.0esr which you appear to have. Firefox 79.0 to Firefox 116 ESR requires macOS 10.12, 10.13, 10.14 or later to run. https://support.mozilla.org/en-US/kb/firefox-users-macos-1012-1013-1014-moving-to-extended-support If you can update your macOS from 10.10 to 10.12 or later then you will be able to run Firefox 115 ESR currently at 115.30.0esr and planned for updates till 115.33.0esr next year unless Mozilla extends again. You can check for macOS updates on the App Store on your Mac though you may need to use Safari when doing so.