I have made the CT editable in the CTHub as suggested, I have recreated the content type and the list it was in from scratch. The content type is set as the default for both lists, both content types are published. When I click new item the OOB form opens with no problems. I am able to create the workflow using the columns from the content type, but I can't access the form editor for anything except the Item CT in either list. I have been able to do this wih other custom content types in my tenent, but this one just doesn't want to work.
Does anyone have any suggestions?