How does it not work?
It shouldn't be launching the wrong game because the version number is the same 3.0.0 that the script is looking for.
If your gbx's aren't opening at all, try repeating step 2 of the tutorial:
Step 2 says:
Select any challenge/replay (either TMF or MP), right click it and select [Open With]. Select your just made .cmd file there, and tick the checkbox at the bottom to always open it via this .cmd file.
This will re-associate the gbx files with the script, just in case the update broke that connection.