I have tried so many workarounds. I have installed all the TDAbleton scripts automatically and manually. I have restarted all the software and my computer several times. I have checked the scripts myself in code editors. I have looked at my Preferences cfg file and the Log.txt file. I installed loopMIDI to try and help, but to no avail. I have triple-checked all my paths and folder structures and also cleared any cache from Ableton. It seems like my Ableton build will not recognise TouchDesigner as a control surface, and it is driving me crazy. Please, can someone with more experience and knowledge help?
I was able to solve it. Instead of installing the TDAbleton Scripts folder in my Ableton User Library, I copied the folder to the default location where the Ableton core installation lives, which is C:\ProgramData\Ableton\Live\Resources\MIDI Remote Scripts. TouchDesigner as a Control Surface finally showed up in the program, and I was able to connect TD and Ableton Live using the tdAbletonPackage.
I have Live 12.4, and I did have an issue with OneDrive earlier in the year, which could have affected where Ableton is looking for my user library. I still don’t fully understand why it wouldn’t pick up my current user library, but since resolving it, it’s fine. Thank you for your response. Maybe this could help someone else.