usb to audio connection

[robmazco]

I have a device for on hold music, via RCA jack its plugged into a usb to audio connector (no name brand). I have the rca jack plugged into a mini adapter which then plugs to the usb to audio Mic port. The usb end is of course plugged into pc. With the on hold box playing, I have no sound is coming from speakers.
The usb to audio connector has a headphone port, when I plug speaker into that, I get sound so I know sound is coming from device, thru rca and out speaker port.
But I get nothing when I plug usb to pc. PC recognizes it and it even has the sound level go up and down with music so its getting the signal.
Any ideas?

 

[robmazco]

This is an On-Hold Plus 6000 unit.
Further testing:
I plugged unit directly into my mic in and line in on pc, with each I can see the sound level indicators going up and down along with music as it plays. But I still cant get it to play thru pc speakers.
Ideas?