I have a Sony Bravia Android TV, a Sonos Playbase 5.1 System with Sub & 2 Play 1's connected via a Flexson HDMI Switch. The optical cable is connected to the Flexson and into the Playbase. I have a single HDMI cable connected to the Flexson HDMI out into HDMI 1 on my Sony TV. A BT Set Top Box is connected to HDMI input 1 on the Flexson and TV is set tp use Audio System in the settings, This gives 5.1 Dolby Digital from the Sonos fine. I have an Xbox one connected to the Flexson HDMI input 2, that also works fine through the Sonos, What does not work is Android Apps installed on the TV such as Netflix, Amazon Video etc...
I have connected an HDMI Arc cable into the HDMI 4/Arc port on the TV and into the Flexson HDMI input 3, there is an ARC button so when I press that and choose HDMI switch 3, a message appears on the TV saying that an Audio System has been connected. If there is no sound then make sure you connect HDMI 4/Arc, there is no sound and the message will not disappear. If I turn off the Arc button on the Flexson, I just get TV Speaker sound only.
I am fairly Tech savy, so followed logic with regards to connectivity, previously I just had a soundbar that was connected to my HDMI 4/Arc on my TV and it just worked. Not sure where I am going wrong or if anyone else has had a similar issue.