Apple TV (4th Gen) surround sound not working with my Marantz SR5011 receiver?

I currently have a 4th generation Apple TV connected to a Marantz SR5011 receiver and for some reason it will not pick up / process any surround sound from my movies. It simply plays the center, left and right channels.

I can play the same movie file through the same receiver with my Xbox One S media browser and the surround sound works fine. Files (.mp4) are not the issue. They also play correctly through Itunes/ Quicktime on my PC which has 5.1 surround.

I even switched the HDMI inputs on the back of the receiver to make sure it wasn't a limitation or problem. I have run through all of the surround sound settings on the receiver as well but no surround sound. I have tried switching the settings from auto to 5.1 on the Apple TV and all other suggestions on FAQ's with same results. All of the other components attached to my receiver automatically trigger the surround sound properly via HDMI (Dish Network, PS4, PS3, Xbox One S). Any assistance would be greatly appreciated.