Pioneer is video, Marantz is audioBoth the Pioneer and the Marantz are receivers. Why are you trying to connect two receivers to your TV?
The Marantz provides surround sound, or it did before we tried installing firestick. We can get sound through the tv speakers but not they the Marantz.The primary function of a receiver, by definition, is to provide audio output, usually of very high quality. Recently, recievers have been expanded to also handle video distribution but they still provide high quality audio output. I’ve looked at a photo of the back panel of your Pioneer model and it looks to me like it provides everything you need. I think your problem is that you’ve got a box in there that you don’t need - the Marantz.