Try powering everything off (TV/PlayBar) (not standby) - leave them off and disconnected from power for 3 minutes and then power them back on again and see if that causes the audio to spring back to life.
Also perhaps check the audio-out in the TV settings is set to the Optical Port and that the codec in use is either PCM Stereo or Dolby Digital and NOT DTS
Other things to perhaps quickly check…
- That the Playbar volume level is not set to low, or muted in the Sonos App
- If you were playing music audio earlier - you might also want to try selecting the ‘TV icon’ in the Browse Tab in the Sonos App (below the installed music services list) in case the audio-out is set to ‘Music audio’, rather than ‘TV audio’.