Hi,
Please try the following steps:
Open Task Manager (press Ctrl+Shift+Esc), look for all Roblox processes, right click on them one by one and select "End Task". Then, press Windows +R to open Run program Windows, then copy and paste this: %localappdata% and hit enter. Look for Roblox folder and delete its contents.
Now, dowload the installer again and run it. In the search bar, search for Roblox Studio, right click on it and select Open file location. Open the folder and look for "RobloxPlayerLauncher" within the subfolders. Run RobloxPlayerLauncher. Let me know how it goes.
Regards.