Streaming not using rear surround

[MNaudi]

I have a denon AVR-X3400H with a Roku ultra as a source. Currently I have two side surrounds and one rear (had two, but one is damaged). I notice on the denon osd that the center rear surround never seems to get used. I’m wondering if this is because of my setup or the source material?

 

[Trebdp83]

If using the Dolby surround mode or any mode + Dolby Surround, a single surround back speaker will not output sound.

 

[MNaudi]

Thanks, that's what I was wondering. I was hoping the reciever could down mix to a mono rear. Time to get that busted speaker replaced.