The Solo2's work correctly when plugged directly into the computer's headphone port - correct?
However if you use a Bluetooth transmitter/receiver pair then you only hear the left side headphone...
May be a matter of the connectivity involved: Your Solo2 cable is TRRS. The Bluetooth wireless must be able to support that connectivity.
Google TR, TRS, TRRS to get a sense of the pinouts that can be used. Should help you determine if your set up is supported or narrow down the problem.