Missing "Assign using active assignment rules" checkbox in "Create Case Queues and Assignment Rues"

Complicated one this, bear with me.

The checkbox was not visible when I create a test case at the end of this lesson, and knew that the rule didn't run because the new case remained assigned to my user. I went back and checked my record type, layout, etc. thoroughly, also that the correct layout was assigned for my user profile. I went round and round in circles on this.

I think I finally fixed the immediate issue of the rule firing because of this tip, although at first I didn't wait long enough after deactivating and then reactivating the assignment rule. Or maybe it was just erratic. Anyway, on about the 20th time of turning on the checkbox in layout properties for the layout, it appeared on the case-edit form, and I was able to edit the case and see the rule fire (because the case owner changed as expected).

But I still can't pass the lesson because it says "We can't find an active standard case assignment rule." Which is odd because I have seen the rule work as above. So it's still being really erratic.

Any ideas anyone?