Cross reference drop down not activating

[GGOffice]

I am creating a manual that is comprised of material from previous documents in addition to new material. When trying to insert a cross reference in the areas that had material that came from previous Word documents, when I click on the cross reference, the drop down does not activate. In other areas, I can easily insert a cross reference. Can anyone help me understand why some areas seem to "suppress" the cross reference function? I am using Word 2013 and when inserting previous text from other sources, I am using the "clear formatting" tool. TIA!

 

[macropod]

If you're pasting as plain text, which your description seems to imply, any bookmarks in the copied content will be deleted. Hence there is now nothing in that range to cross-reference.