I recently came across an issue while helping the customer remotely. The issue was that the “sound sticks” were not recognized as reported by the customer. However, this really wasn’t the issue.
BUT if your sound sticks are not recognized, and they are connected over USB then you may try the following solution:
Unplug both the power of the speakers and the USB port, then reconnect power first, then USB and check if they are then recognized.
Upon further inspecting and analyzing, i found out that the speakers were connected correctly but since the customer was also running Apple TV connected via Airport Express, the sound from iTunes went to Apple TV instead of speakers. If you run into this issue, then simply click the speaker icon on the iTunes and change the Output to Computer.