Don't Use the "No Markup" Option in Track Changes
Word versions 2013 and later include the No markup option when working with Track Changes. Do not use this feature if you are also using the Citavi Word Add-In.
The option Track Changes makes your changes look as if you had already accepted them. However, text that you change is still present but is simply hidden from view. When this option is selected it's possible that a reference that you inserted with the Word Add-In and then deleted is still present in your Word document. This keeps Citavi from being able to apply certain citation style operations related to ambiguous references or reference numbering.