Firefox 116.0 to the current 147.0.4 and 140.7.1 ESR requires macOS 10.15 (ten.fifteen) at minimum to run so the macOS 11.7.11 you have meets the minimum. https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac https://www.firefox.com/download/all/desktop-release/osx/ https://www.firefox.com/download/all/desktop-esr/