Not familiar with this exact model, but we had someone at the local repair cafe come in last week with a similar Logitech set complaining about the opposite: only sound out of the woofer. Issue was cabling. The woofer had a 3.5mm jack for input and a 3.5mm socket for the speakers. They had their own 3.5mm jack that needed to go in there. In their case, the user hadn't connected speakers to woofer. Could it be than in your case there is a similar setup and you connected the speakers directly to your sound card, rather than via the woofer?

Another possibility: a lot of these woofers have a tone knob on the back, basically managing woofer volume. If that is turned all the way off, you only get output out the speakers.

Does it have seperate woofer input?

only 3 inputs ; in , out and earphones.

Its a passive sub woofer, means its getting its input from both sound channels, if the woofer isnt working then it likely its got a bad connection inside the box, possibly a loose wire or dry solder joint. Might be worth opening the main unit and checking out the connections and solder joints, its rare for a woofer to die but they too suffer from the same issue as most older permanent magnet speakers do and the internal wiring of the speaker itself breaks.

If the woofer has a daughter board in the main unit its also worth checking the caps on that board making sure they are ok.

I remember haveing one burned out , don't remember exactly the part that died... resistor?hmm I need to remember.