Firefox (V-91.0.1) stopped working immediately after uninstalling the Mozilla VPN with an error “Code execution cannot proceed because Vcruntime140_1.dll was not found." I unstalled and re-installed Firefox several times, but the error persisted. After reviewing feedback from other users with the same problem on the Firefox support website I looked for the Vcruntime140_1.dll file in the \Program Files\Mozilla Firefox folder on 2 other Windows 10 systems on my network with Firefox (V-91.0.1) running successfully, but it was not on either system. All 3 systems are 64 bit running Windows Version 21H1. However, I was able to locate a version of the "_1" file (size 44.7 kb) in the MS Edge folder located in \Program Files (x86)\Microsoft\Edge\Application\92.0.902.73. I copied the file from the Edge folder to the \Program Files\Mozilla Firefox folder and Firefox has been working fine for 2 days now, I can only hope it continues to work properly.

At this point I believe there are 3 issues that need to be understood. 1.) This will probably happen to other people and should be addressed in the Firefox install software. 2.) The problem created by the Mozilla VPN uninstall software needs to be understood and corrected. 3.) Why don't all systems of what appear to be the same configuration require the "_1" file.