I added a new sharepoint choice field to my list. I already had an existing nintex form for that list. I added an new choice field to the Nintex form. When I try to connect it to the sharepoint form, I get an error "The server encountered an error processing the request. The message is 'Object reference not set to an instance of an object'". I might add a horribly formatted error message with a bunch of embedded HTML.
Any idea what causes this??
I dragged it from the List Columns and that appeared to work. But still does not excuse the fact I can't just connect an existing nintex field to a sharepoint field.
I know this is quite a bit late but I'm having the same issue. I made a web request control and when I set the "ID Connected to" field to any of the SharePoint columns it lists in the box, I get this same error. Does not happen when selecting "Text connected to".