We install the ruby files in your User AppData folder. If you installed as another user, those files may have been installed in that other user's AppData folder and not yours. If that is the case the plugin will not be found by SketchUp

Here are some instructions to check the installation location:

First, use the SketchUp Ruby Console window:

to find the location of your SketchUp plugins folder by typing:

Sketchup.find_support_file('plugins')

and then click on "Enter". You should see something like this:

for you, it should show:

C:/Users/[Your user Name]/AppData/Roaming/SketchUp/SketchUp 2015/SketchUp/plugins

Look in that folder in Windows File Explorer, and make sure there is a folder called RPS_IRender_nXt and a file called RPS_IRender_nXt.rb:

Note: If you don't have the View option for showing known extensions un-checked, you will just see the file as being named "Rps_IRender_nXt".

Folder View Options:

If that file is not there, then you will need to reinstall IRender nXt and make sure that the Ruby Plugins folder get installed into your AppData folder.

If you do not see your user AppData folder shown here during the install:

then you may have to go back and use the Browse button to select your folder:

After reinstalling, or if that file, RPS_IRender_nxt.rb, is already in that folder,

C:/Users/[Your user Name]/AppData/Roaming/SketchUp/SketchUp 2015/SketchUp/plugins

After installing, if IRender nXt still does not load, please do this:

Type (you don't have to use the proper upper and lower case letters for this to work)

load 'RPS_IRender_nxt.rb'

in the ruby console window and tell me what appears.

Then type in:

load 'RPS_IRender_nXt/RPS_IRender_nxt2.rb'

and copy all the text that appears in the Ruby Console and send it to us.

Hopefully all of that will give us a clue.