Can't uninstall old version, can't install new version
My computer (Win10) has an installation of FortiClient Endpoint Security (4.2.5.0286). It doesn't work, not sure why. So I want to install a version that will work, but I can't, because the previous version is installed. When I right-click on this in Apps & Features and select Uninstall, it claims that "The Feature that you are trying to use is on a network resource that is unavailable", and asks me to point out where FortiClient_x64_en-us.msi is located. I don't have such a file (I've checked), so I'm wondering what can be done to blow away the old installation before I can install the new version.