I am using Nintex WF and Forms 2013 (trial version for now) on premises and have created a SP library with only one content type, a custom content type based on a document set with extra columns pertinent to our use case. When I try to create a Nintex Form for this content type, I get this error message:
Error - Cannot use Nintex Forms for content type : <my custom content type>
I have tried the same for the standard Document Set content type as well as the Folder content type and get the same error. I can successfully do it with a simple custom content type based only on Item, but have not determined what degree of difference between there and my desired custom content type causes the error.
The only post I've seen related to this seems to indicate that someone figured it out but I do not see how they did it. It referred to the content type being marked as read-only possibly causing the problem, but that's not my situation.
Does anyone have any suggestions?