I'm guessing you have the PS2 SG, since there is no red Les Paul guitar.

What adapter are you using? From what I understand, only a few specific adapters work with guitar controllers (the ones that don't work will detect in Windows, but it won't respond properly to all buttons).

Taken from the Discord (!ps2 command):

Here are some PS2 to USB adapters we can recommend for PS2 GH guitars:
- Kebidu PS2 to PS3/PC Adapter: https://bit.ly/2AntnFB (Whammy may not work correctly. Does not work on Mac.)
- Raphnet PSX to USB Adapter: https://www.raphnet-tech.com/products/psx_to_usb/index.php (100% compatibility across all operating systems. Whammy works just fine.)

Here are some more adapters that we can't 100% recommend just yet, but seem to work fine:
- Xahpower PS2 to PS3/PC Adapter: https://www.amazon.com/dp/B097MXJ1BW (Whammy does not work correctly, see notes below for fix. May also outright not work until said fix is applied. Does not work on Mac.)
- Hyperkin M04196-BULK PS2 to PS3/PC Adapter: https://www.amazon.com/dp/B09GS6NXVS (Reportedly supports whammy correctly. Does not work on Mac.)

Your mileage with other adapters may vary. Be sure to read product descriptions and reviews to get an idea of their quality.
NOTE: Please do not order the Mcbazel PlayStation 2 Controller to USB Adapter for PC or PlayStation 3 Converter Cable from Amazon, as it explicitly states it does not work with Guitar Hero guitars!

Alternatively if you're feeling crafty, you can make a PS2 adapter yourself with an Arduino using this app/guide: https://sanjay900.github.io/guitar-configurator

(Small sidenote on the Arduino part, use a Pi Pico instead. It's cheaper, more available and works with the same guide/software).