You can check for issues caused by a corrupted or incomplete Visual C++ installation that is missing runtime components (Redistributable Packages) required by Firefox, especially VCRUNTIME140_1.dll. See "Visual Studio 2015, 2017 and 2019": *https://docs.microsoft.com/en-US/cpp/windows/latest-supported-vc-redist *https://aka.ms/vs/16/release/vc_redist.x64.exe *https://aka.ms/vs/16/release/vc_redist.x86.exe You may also have to install the Visual Studio 2013 Redistributable Package. You need to reboot the computer.