Then I would suggest looking into the texture properties. If other ships show the normal maps, then either the game doesn't find that particular normal map, or there's something wrong with the texture (like lack of alpha channel).
Also, using dxt5nm is something I deeply dislike. First of all it's an automated shortcut to a very simple procedure in swapping the places of the channels in the image, secondly it forces the use of dxt5 compression which is, with some normal maps (and especially with shiny ships), something that affects the quality quite a bit in the negative direction. I much prefer hand-managing the channels, because that way I can select the compression if it suits the map, and uncompressed formats still work if necessary.
TGA works just fine for viewing WIP normal maps as long as you move red channel contents to alpha channel... it doesn't need to be in DDS even.
Also, if the texture itself actually works, using higher scale value in converting from height to normal map might help.