There is a thread on the GameMaker forums where everyone has been asking and discussing Eclipse: https://forum.gamemaker.io/index.php?threads/eclipse-light-engine-pbr-lighting-f...
You can also just ask here if you want or email me badwronggames@gmail.com
If you are importing it into an existing project with many things already going on you may need to setup a bit of inheritance or the light wont have anything to hit. Everything drawn should inherit from a type of the __game object so that their normal map and material maps are drawn. Or if its a shadow caster use one of the various __shadow type objects to inherit from--depending on shape.
If you use tilemap or asset layers they should be setup too as shown in the first basic setup video and mentioned in the User Guide: https://drive.google.com/file/d/1dOVpNrsVvod9C8GMnuO6_hSj5hGVmVM-/view