The Python interpreter neatly tells you what is wrong: you are trying to use a starred expression where it is not possible. There is a lot of Python documentation easily avaibale online. Many times you just need to make a research with your error message to find help for debugging. Also use markdown tags to format your code you are posting or it's not usable. Refer to the documentation about this and more: https://docs.codewars.com/training/troubleshooting/#post-discourse

Given that the oxford comma is debated, I'd prefer if both versions were accepted. Although, my preference doesn't matter in this case and I did complete the task as asked. Thanks.

There have been many debates about the use of the oxford comma, but as far as "correctness" goes, they're both gramatically correct. However, the problem speficies that you return the answer without the oxford comma, so if you include it, your function is wrong.