I think I mentioned this already, but that's not an A2DP headset. It's a SCO headset. That's why it doesn't work. It isn't designed to work yet. We've got a ticket for that, but I'm not sure if it will ever get worked on by me as I don't have a whole lot of interest in supporting mono headsets right now:
https://www.guardiani.us/projects/kagu/ticket/17