Message: Cannot reflow this page because it contains interactive annotation(s).

I had converted a 4 page form to an electronic form and this message appeared: 

Cannot reflow this page because it contains interactive annotation(s).

I now can't edit the form fields or make any changes. The help pages aren't helpful and I can't find in the Preferences where this might be impact on the form. Can someone help please? As usual, this has occurred when I am on a tight deadline!!