[THEBERBSTER]

Hi alex
Sorry I was not able to give you an answer previously due to circumstances beyond my control, the wife.

Your current SH5.exe v1.0.5 try running it as an administrator.
Post #74 Run Both SH5.exe And Ubisoft Game Launcher Application's As Administrator's
Now try.
Post #5 Update SH5 From v1.0.5.0 To v1.2.0 Immediately After Installing

Failing that I would suggest a few things if possible.
Uninstall your new download if it has installed in C:\Program files (X86) folder as this is a restricted directory.
Try installing in this sort of path. C:\Ubisoft\Silent Hunter 5

I would suggest that you uninstall the game launcher from the control panel's program and features.
Always use a registry cleaner after any uninstalling and then reboot your system.
Post #70 How To Use The Free Registry Cleaner 'Ccleaner' > Includes Download Link
Download a new game launcher here and you can install it anywhere, lets say C:\Ubisoft
Post #97 SH5 Game Launcher Install It Anywhere On Any Drive
Hopefully one of these solutions will work for you.
Peter