Latest ultra player connected to new Denon AVR via new high speed HDMI cables. Player set to output DD+. Sound leveling turned off. Get full 5.1 surround playing Amazon Prime Video. Other services like Acorn MHZ Plus and Philo only play in 2.0 stereo. Denon shows receiving DD+ and all 5.1 speakers as active. No sound from center and rear surround speakers. Can’t figure why this is occurring. Not an AVR problem because 5.1 works with other sources and with Amazon Prime played thru Roku. Old Pioneer receiver with optical input from Samsung TV and HDMI from Roku to TV reliably gave 5.1 surround with all Roku apps. Can’t figure out what’s up with current setup. Unless there’s a viable solution just going to give up and live with it.
When using an AVR that supports all the audio codecs, you need to set the Roku audio to Passthrough, not to a specific codec. Don't set it to Auto either. When you have it set as you do the Roku is converting everything to DD+, regardless of the number of channels actually available. With it set to Passthrough, whatever you are watching will be sent to the AVR as is, which is what you want when using an AVR.
When using an AVR that supports all the audio codecs, you need to set the Roku audio to Passthrough, not to a specific codec. Don't set it to Auto either. When you have it set as you do the Roku is converting everything to DD+, regardless of the number of channels actually available. With it set to Passthrough, whatever you are watching will be sent to the AVR as is, which is what you want when using an AVR.