I know that the Entity is properly registered. I gather that the Custom Renderer is also registered properly otherwise there would be no in-game visual at all. The linked are my Model and Render files respectively.
And what exactly would you do for initializing a new RenderNPC without a RenderManager? Because the reason I set things up the way the are presently is I would either pass in a RenderManger or I would have to get the Minecraft RenderManger.
Don't use RenderingRegistry.registerEntityRenderingHandler(Class<? Entity>, Render<? Entity>) (called in init) in 1.8.9, it's been deprecated in favour of RenderingRegistry.registerEntityRenderingHandler(Class<T>, IRenderFactory<? super T>) (called in preInit).
IRenderFactory is an interface with a single method that returns a new instance of the appropriate Render class.
If you're targeting Java 8, you can use a method reference to pass your Render class's constructor as an IRenderFactory, e.g. RenderNPC::new (only works if the Render class has a constructor that takes a single RenderManager argument).
If you're targeting Java 6 or 7, you'll need to use an anonymous class or a regular class instead.
Edit: It looks like you're already using IRenderFactory. If you set a breakpoint in the RenderNPC constructor or getEntityTexture method, are they ever called?
Please don't PM me to ask for help or to join your mod development team. Asking your question in a public thread preserves it for people who are having the same problem in the future. I'm not interested in developing mods with people.