If you see this, you probably have not installed "Animation Nodes" addon, which is required for Neon Generator to work.

Here is how to solve it:

To use Neon Generator you have to install "Animation Nodes" addon,
but Neon Generator itself is just a .blend file and must not be installed.

Follow these steps:
1. Install "Animation Nodes" addon.
2. Open .blend files included in .zip archive.

Where to get "Animation Nodes" ?
https://animation-nodes.com
https://github.com/JacquesLucke/animation_nodes/releases

Some of the reasons could be:

1. Nurbs paths are not supported. All curves have to be Bezier type!
   
   
2. Please check if you have deleted "NEON_OUT" collection or it's contents.
   Neon Generator does not create new objects, it modifies contents of already existing ones.
   You can set in which objects outputs will be generated in the bottom part of *NEON_generator node.
   By default it's set up like this.