I had this same issue and managed to resolve it by making sure the item I was editing had the correct prefix for the armor type (for example, a human male glove in my case.) It had a custom name, but by renaming the visual resource in the create and view resources tab to HUM_M_ARM_WhateverYourModisCalled it was able to recognize it. Some other issues that might be related or you might hit later include assigned the proper slot id (gloves in my case) in the options panel in the resource editor (with your resource selected.)
Possibly unrelated but also something I wanted to document in case you run into it is that if the mod turns the limbs invisible, try leaving the Vertex Color Mask slot in that same panel blank. A lot of tutorials insisted assigning it to a body part but when I did that only the part of the model that had geometry was visible. Not a problem if your glove is bigger than the hand, but I was attaching Bagh Nahk claws which left the entire forearm transparent aside from the claw.
Hope this helps!
