I try to install Gas Masks of the Wasteland, and it starts to unpack in the NMM, gets to 50% completion, and brings up the menu to select AWKCR, NAC compatibility, ect. I chose all of the correct files, and then it says, "A problem c install" in the mod activation queue. A text box says, "A problem occurred during install: Object reference not set to an instance of an object. The mod was not installed". Any idea what could have went wrong?

I have a theory. It happens to me when I try to install EVE. It has something to do with the antivirus preventing you from installing the mod. What you need to do is temporarily disable your antivirus program(s). Then you should install the mod, and it should install fine. This is a case that has happened to me a few times with EVE. Just remember to re-enable antivirus. I hope this helps and if it does not, please ask and maybe we can find another solution.

I hardly trust NMM for installing mods for anything now, as I've always experienced issues with installs and data loss. What I can recommend is you install the mod manually and then activate it through NMM instead.

@stoobygacks @Chromesthesia Thank you for your reccomendations, I shall try them in the morning.

Yep, you should probably do what Chromesthesia said. To install it manually, go into your game folder (where you installed your FNV) and once you're in the folder, go into the data folder. Open up the file you downloaded (Gas Masks Of the wasteland) go into the data of that folder (If there is any) and drag the meshes, textures, and, esp to the Fallout New Vegas folder I mentioned earlier. I hope you can Install Gas Masks of the Wastes soon!

It can't handle large installs very reliably. When I realized that it was going to happen with most big mods, I went to mod organizer 2.