If you have some incomplete references in your EndNote, e.g. without a DOI number, or a reference without volume/issue numbers or page numbers, you may use the Find reference updates to update these references.
Select the references required a update
Go to References > Find Reference Updates
A pop-up box will appear to show the new fields that may require updates: the right column is a reference in an EndNote library with an error in the title and a missing journal field. You can select Update Empty Fields to add the correct information in the left column to the reference in the right column.
Use the three update options in the middle accordingly.