Hi,
I assume you have made sure both the B2 and headphones are in pairing mode ?
Which version of the B2 software are you using ?
The B2B version offers better Bluetooth connectivity.
Brennan now do not market the B2 as offering Bluetooth output but it does still work for a lot of devices.
If you cannot get your Sony headphones to work then as an alternative to buying different headphones you could connect a Bluetooth transmitter to the B2 via optical.
This is one option
or this
John