Created new module, now all products get 404 not found

After following this as a guide: Github module for grouped product attributes

Now all my product pages give a 404 error.
I am attempting to add all of the attributes to the grouped product collection so that I can access custom attributes from the grouped product page.

I’m not sure how to evaluate where the problem is and/or how to reverse course.
Is there a log file to see what the error might be?
Or can someone take a look at the github link and let me know if that should work?

Any advice?