I believe this is almost certainty a design problem with the speakers. I also have this problem. Not only does sound not come out at all but in my case, sound only comes out of the right speaker with the power knob on it, the left speaker is silent. I've figured out the problem is the knob, it seems to have trouble "engaging" properly because it is far too loose, it has too much give to it. By fiddling around with the knob, jogging it left and right, back and forth, I can eventually get the sound to come out of the left speaker. But the knob is very sensitive and make any subsequent adjustment to it, for example, by changing the volume, and the left speaker cuts out again. That's why people are able to get the sound back by turning the power on/off; eventually, the knob completes the power circuit like it's supposed to and it works but a lot of times, it doesn't. All in all, a very frustrating and disappointing experience.