Sounbar to TV mystery


Oct 30, 2012
Connected Vizio soundbar SB2920-C6 ( a 2010 Panasonic TC-P46C2 TV (
Followed instructions carefully. The only clearly marked as "audio-out" jack on the TV is a Digital (optical) audio out which I used to connect to the same on the bar. When playing over the air regular antenna TV channels,there is no sound , and the bar's input LEDs flash rapidly, which is supposed to indicate an unsupported format present. (no idea what that means...) Also from the manual, the TV may be set to variable audio output, so reset it to a fixed or standard one. How? Where? .
Vizio manual suggests for this problem selecting "Audio out or Digital Out" in the TV's audio settings, but I do not see such in the menu, and neither the one to set a setting to PCM.

YET - there is sound without fussing with the menu and settings when the TV is set to HDMI1 or HDMI2 to stream content from may PC via HDMI cable.

Is there a way to to get that sound going?