Hi,
since the TGP is an optical/electro-optical targeting device, poor visibility affects the TGP.
Could it be that the line of sight from your aircraft to the destroyer is obscured by clouds or fog?
If this is the case, you will not see anything with the TGP, even with the BOW/WOB mode.
So the idea of eyeballing the destroyer and then verify the TGP video is a very good suggestion.
Hope you get it figured out.
cheers
Magic