Case Configuration - "Start date missing"

I’m having difficulty setting up the case process. It will not allow me to save the process because the ‘start date’ is missing. There’s no field present and I’m unable to save the configuration.

Any ideas what this could be?

D365 For Operations Enterprise Edition

Can you show us the actual action or task within the process you are trying to create and not the categories - the task or action has the setting of a start date in days which it adds when creating them as part of the process. This is the actual task/action for people to undertake within the given process.