Roku connection thru an AV Receiver

I am having a strange problem. Prior, I had a Smart TV, (non-Roku), connected: DirecTV> external Roku> connected via HDMI, to an AV 7.1 Receiver> and then to the TV. (HDMI-eARC, on TV and AV). The system worked perfectly; and the sound was unbelievable. (TV setting>SAT/CABL.......Roku setting> StreamBox)

Here is the strange problem:

I have purchased a Roku TV. (TCL). which eliminates the external Roku Unit. All other connections are the same as before; except there is no need for the StreamBox HDMI; as it is a single connection to the TV. (Internal Roku).

The Surround Sound (AV) works with the DirecTV channels; but when I go to the Roku Streaming channels, (Netflix, Prime, Pandora, etc);  THE VIDEO IS FROM THE STREAMING CHANNEL; but THE AUDIO IS FROM THE LAST NETWORK CHANNEL WHICH WAS ON.

I have spent over 12 hours on chats with the manufacturers support people, (Roku, TCL, Sony); and have received "NO" help. Each of them tell me to speak with one of the others. I can't be the first person to ever have this problem!! I think it has to be a setting, but I have tried a bunch of them.

Can anyone help me??