Have you placed the install.ps1 script in the same directory as the installer .zip file you downloaded from the link in the first message in this thread?
You might want to try opening a PS session and running the script in there so you can see any errors messages that may be generated.
If I run the install.ps1 script without any other files in it's directory, the first complaint is that it can't find a mounted Kobo ereader.
Code:
Couldn't find a Kobo eReader volume! Is one actually mounted?
* Nothing to do! Press Enter to exit: