After searching GitHub I found an additional library.

After adding this library:
https://github.com/TinyCircuits/TinyCircuits-ATtiny841-Library
I was able to get the code to compile.

I would recommend adding links to ALL necessary libraries to the instructions.

Oops, sorry about that!

The ATtiny841 library was the hold-up on the premium kit program and since we are in the process of changing everything over to fit that library, I missed that in testing since I have the library installed here.

That will be fixed immediately across everything!

Thank you for bringing that to our attention