Won't work

[AustinVR27]

[Yusarina]

Make sure you use the dev version of cats:

https://github.com/absolute-quantum/cats-blender-plugin/tree/development
Direct link to zip file: https://github.com/absolute-quantum/cats-blender-plugin/archive/refs/heads/development.zip

The current released versions will not work blender 3.6 or 4.0.

Also Blender 4.0 is also not supported by cats due to the fact cats has no been updated plus MMD tools which cats uses is outdated. I would either find a unofficial cats version which supports blender 4.0 or downgrade to blender 3.6.