Speakers not working on any device
A month ago I bought Genius SP-HF160 speakers. Today I tried plugging them in my PC, but they don't work. When I plug them in, the small light at the backside of the speaker should turn on to indicate that the speakers are connected, but it doesn't. And there's no sound coming from the speakers, even after I turn the volume to the maximum. However, Realtek notifies me that I've plugged a new audio device in the PC.
I tried plugging them in my Sony Xperia Z Android smartphone and basically the same thing happens - the light is not on, there's no sound coming from the speakers, but the device seems to recognize that something is plugged in because there's no sound coming from the phone's own speaker when these speakers are plugged in.
It feels as though as there's an on/off switch somewhere, but there's not.
The problem is that I bought these speakers a month ago and I've lost the check in the meantime, so I can't return them to the store and ask them to replace the speakers or to examine them. If anyone has some suggestions on what could be wrong with the speakers and how could I fix it (preferably for free), I would be very grateful!