With your armor in NifSkope, open the NiTriShape on which you are changing the texture. Expand "BSShaderPPLightingProperty" and then expand "BSShaderTextureSet". In the bottom display, expand "Textures" and make sure the path to the texture is correct. From your screen shot, it appears the path is not. Left click on the "flower" next to the textures string and a small window will open where you can select the texture file. Click "OK" Save the corrected .nif file and exit.

Check in game to ensure everything is working. Don't forget to toggle "Archive Invalidate" in your mod manager.

I did not download the .nif since I would not have the texture set for this armor.