I decided to report an old problem again. I have never been able to connect TCL 49S405 with Yamaha RX-V575 using HDMI ARC and Dolby Digital Plus. It works with straight Dolby Digital, DTS but the moment I select Auto Detect or Dolby Digital Plus, I lose all sound. I even lose the beeps when moving around the menu so it is not specific to any particular channel. It is either Roku TV or Yamaha AVR problem.
The AVR is detected and documented as DD+ capable and there is a way to re-sync Dolby Digital Plus connection temporarily. I have to cycle through the AVR inputs and back to AV4 (ARC) to recover DD+ audio but only until a stream switches to something else like another channel or an advertising block when the DD+ connection is lost again. It feels like this problem has a simple software fix - TV an AVR must communicate when the stream switches. As a workaround I am using Dolby Digital (without Plus) because re-syncing manually is not practical.
I had this problem since 2017 and it has been reported with other receivers and sound bars by many people, search this forum for DD+ or Dolby Digital Plus. I understand why this might be a low priority bug - who'd use a budget TCL TV to set up a home theater with an AVR, but still. This might be Yamaha AVR problem - if you have DD+ working with another receiver, please do reply.
Let's hope that we'll get some attention from Roku engineers this time.
This AV forum thread indicates that other non-Roku TV brands have exactly the same DD+ issue with my Yamaha receivers. This certainly points towards the receiver as the culprit.
HDMI® ARC is disabled by default. To enable HDMI® ARC, in the Home screen menu, navigate to Settings > System > Control other devices (CEC), and then highlight HDMI ARC. Press OK to enable or disable the feature.
All audio is fine with my Yamaha, but I stay away from ARC. Maybe, if it turns out to be the set up, try getting your audio another way, not back from TV, but from Yamaha and only send video to the TV.