Hi @TcKiddco , Most likely the assignment group you are trying to create is already been created with the same name, you can check that from "grpups" and find the name using filters in the native UI. 

1. Delete the existing assignement group and create new.

2. Make the existing assignment group as inactive and create new with your name requirement.

If this solution helped you Please Mark this solution as accepted and helpful as it will be helpful for other users as well.
Best Regards.
Saurabh V.