INSIGNIA TV WITH ILIVE BAR. 1 SIDE WORKS
Try swapping your cables from the sound-bar to the TV. If the sound still only plays through one channel but the channel has changed from right to left or vice-versa, then you have a bad cable.
If the performance is the same, connect a different device using the same cables to see if it's the sound bar input or the TV output.
Once you know where the problem is (the sound bar, the TV, or the cables) you'll know what unit needs repair or replacement.
It is entirely possible that a solder joint for the sound-bar has come loose. A soldering pen would easilly fix this if it's a bad joint/connection.
Hope this helps!