Check the audio menu in the TV and see if you can change the audio output type.
If not then you could use an HDMI input selector with audio extraction to bypass the TV for external sources.
Same issue. I have SONY Bravia Android TV, and when i connected optical wire to my 5.1 then only front speakers and subwoofer works. now i am using stereo cable and prologic on my audio system.
Check the audio menu in the TV and see if you can change the audio output type.
If not then you could use an HDMI input selector with audio extraction to bypass the TV for external sources.