I'm trying to add a gold tinge to the Akaviri katana. I copied the old nif and changed the texture paths inside it using nifskope (the texture shows up fine in nifskope). I've also made a new item inside the CS and change the nif path.

It shows up fine in the CS, the texture and the nif load with no errors or anything.

However when I start the game, the texture is the standard akaviri katana texture.

I have _n and _m dds's in the folder with my main texture (though I haven't edited them), I'm 100% sure the texture is a relative path to the correct texture.

What am I doing wrong?

Do you have the Bethesda texture packs installed? These 2 texture .esps were causing my third party textures to not appear in game at all. Disabling them fixed the issue for me.

Nope, they're disabled. I also deleted the bsa's and the esp's as well just in case, still nothing.

Have you created a new texture set for your new textures?

For my retexture mod I created a new texture set, then had the item I added link to the new textures and it seems to be working so far. I haven't tried changing the nif via nifskope and then enabling that in the CK, so i don't know if there is a way to get it to work that way.

To add a texture set go to: Object Window->Miscellaneous->TextureSet.