A family of Microsoft word processing software products for creating web, email, and print documents.
It sounds like you might be starting with a document that has been converted from a mail merge main document into a normal document (which is something that is done by the merge tools add-in). If that is the case, the mergefields may have been converted to DOCVARIABLE fields. You can tell if that is the case by using ALT+F9 to toggle on the display of the Field Codes.