That error almost always happens when the mod has not been installed correctly.
Firstly: make sure to follow the KittyPatcher mod installation instructions noted here:
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Troubleshooting tips:
0. Confirm that your gangbang mod file has a .mod file extension instead of .txt!
1. Make sure you're using a new, unmodified, vanilla CourseOfTemptation.html to install the mod
2. Ensure that you've deleted your existing `logs` subfolder before you run KittyPatcher.exe
3. Make sure you're using the currently supported KP & Game versions:
KittyPatcher Version 0.1.4 & CourseOfTemptation Version 0.6.3d
4. If all else fails: Start from scratch with a brand new folder for both your CourseOfTemptation.html + mods folder (this will fix the error in some rare cases)
5. Also, if you're using a browser to run the .html: I've only confirmed that the mod is working on Mozilla Firefox, so make sure to use Mozilla!
Hope this helps! Let me know if it doesn't and I can help you troubleshoot further.