Are you letting the installer run as admin? Like many things, it will need that to be able to install itself to program files because of how modern windows security works. And the launcher itself will need to run as admin as well for the same purpose - installing the games.
If you are already running as admin, then there are a couple things it could be. I'm not an expert or anything, but I've seen positive results by clearing out the launcher's storage locations.
C:\ProgramData\W3D Hub\ -> This is where the launcher puts files to update the games, dependencies, and its own update files.
C:\Users\YOU\AppData\local\ -> This is where the login info is cached or something, probably won't help anything in this case, but I've been wrong before.
Try these and post back if anything changes. Thanks.