I also have a similar issue. I download mods just fine, but some mods just won't install. Like today, I was able to install the Mosin Nagant, but I still have trouble installing Nightstrikers, Crafting Fury 9000 GTX, and certain texture mods.
Alright so I'm having an issue with activating/installing certain mods while I can can still activate others. Whenever I try to activate them, I look for the "Mod Activation Queue" tab on the bottom of NMM and under where it says status, it says "a problem occurred during install." Mods that fail to activate include: Nightstrikers Snap 'N Build Harley Quinn Outfit CBBE f4se Crafting Fury 9000 GTX