I don't know which exact set of Soundsticks you have (Harman Kardon has revised them a few times over the years and the connections may have changed), but my guess would be either a damaged wire or the wires not plugged in right. The power on/off button on the back of the subwoofer doubles as a volume button, but I think it only affects the sub's output. Double-check it anyway.
Glad you got that sorted. It didn't occur to me to suggest checking those buttons since you said you just moved the sub part. Anywho, I hope you enjoy the Soundsticks. I have an older set and they are quite easily one of the best sounding 2.1 computer speaker sets out there.