I have no freaking idea what is causing this. I'm positive I wont get through this one on my own any help is appreciated. I am losing my mind every time I get through an issue theres another one just waiting for me. Ive felt like peter pan for the last couple hours just trying to stitch my shadow back on.

ingame not attached to skeleton:

blender pic Im so confused :

Ive tried unparenting everything, deleting skeletons, parenting in different combinations, combining all the meshes, weightpainting manually, autoweightpainting, attaching the meshes to individual bones, etc. nothing works I always get the same result of the meshes not being attached to the skeleton. I started off with pasting branches into nifskope onto the default male body. At first I thought it was because the mercgrunt outfit was made for humans so thats why it was attaching to the skeleton normally and the other meshes which are made for nightkin werent working.. but then I noticed a piece of the nightkin mesh did actually attach correctly like the mercgrunt outfit and I am extremely confused why that one piece of the nightkin mesh is attached and the others are not

my first guess is still that the animation weights are getting messed up when saving the final output. if you're weighting in blender I have no clue. I don't use it. but the nif only allows for 4 bone influences per vertex. so if the weighting ends up with more than that things get discarded and distorted. Also if the nif biped isn't replacing the base body, and is being overlaid, then you have to make sure the relative weights of your armor match the body. same with any other pieces that may be used.

Try using outfit studio to copy or paint bone weights, its not accurate 100% but you might get better results.