I’m somewhat confused, the Port has no TV input to switch to.

if it is a Sonos Amp, instead, which does have a TV input, is the TV stream restarting? The auto play switch will only activate when the stream to that input starts, it doesn’t switch over if the data has been active while the system was on another input. It triggers on zero to X, not on stopping of the other stream. 
 

The onkyo receiver is certified “works with Sonos”, the port is connected into the analog input CD. Therefore, since the receiver has the “works with Sonos” badge it can automatically change the output from the receivers main hdmi output (tv) when it senses music playing from the Sonos app while keeping the receivers main hdmi output (tv). When I stop music on the Sonos app, it does not automatically change back to the receivers main hdmi output (tv) sound, I have to manually change it on the receiver. 

Ah, I see. Your best bet would be to contact Onkyo, since it is their receiver that isn’t operating properly, not the Sonos. 

Yeah I was hoping to see if maybe it was something with Sonos, maybe just pausing the music isn’t enough? I’m not sure. Thanks

No, Sonos has no input on the way the receiver switches inputs back and forth. The receiver would be the thing that detects an input from the Sonos and switches to that input, but again, that’s an Onkyo thing. Wouldn’t be anything in the Sonos software.