Creating forms notification 'No new form field annotations were detected'

I am trying to create a form from a PDF which was created in Indesign. I have been doing this easily for years and using the same document with updates every year but for some reason it won't work this time.

Acrobat Pro won't automatically scan the PDF for fields and this notification comes up 'No new form field annotations were detected'. It's usually a simple process. It's a double page form with a lot of fields so I don't want to manually do it myself. 

Thanks

Lucie