Hi Fagenmcdowel,
Where does that error occur?
You can follow the full code here: https://github.com/vcerqueira/blog/blob/main/posts/dl_for_forecasting/univariate_ts.py
I'm using Python 3.8 and keras 2.9.0. Note that there are some custom functions from a src module that is on that github repository.
Let me know if this is useful. I'd be happy to help more if it still doesn't work.