A ported model, eh? I'm not sure if helping with ported model doesn't break any policy here, if yes, then mods feel free to edit/delete my post.
From what I see in the .mdl, the only needed textures are
twighlightdragon_ChangableTexture1.blp
twighlightdragon_ChangableTexture3.blp
twighlightdragon_ChangableTexture2.blp
and they require no path (i.e. you delete war3imported in the import menu)
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anyway, do you really need model that takes 3mb of your map?
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EDIT:
Made a test map where i imported that model. Works fine, model shows.
Make sure you didn't accidentally delete part of the textures' / model's name