Hello @Cameron_R!
I spent a bit of time going step by step on the implementation for the Community Workaround you’re using and was unable to figure out the bug myself. When I created a page fresh from scratch, I was able to use the JS and CSS no problem to create the multi-step form and it seems as though you’ve used this on your other pages as well. It does look as though this question came up for another user about a year ago based on the comments in the original post. I wouldn’t say the script is broken, I would recommend building out a new page in the classic builder (not duplicate) to see if this solves the issue.
If you’re looking for another workaround in the interim, here’s two other versions of Multi-Step Forms that may be of different format but could be an alternative to see if it works for your current page.
Multi-Field - Multi-Step Form
Add A Multi-Step Form 2.0