Comment 82 for bug 1438510

I had the same problem and can verify the same workaround with the following:

pulseaudio-git v7.0.34.g9d2b763-1

bluez 5.34-1

Device 00:1F:82:28:93:51
 Name: DR-BT101
 Alias: DR-BT101
 Class: 0x240408
 Icon: audio-card
 Paired: yes
 Trusted: yes
 Blocked: no
 Connected: yes
 LegacyPairing: no
 UUID: Headset (00001108-0000-1000-8000-00805f9b34fb)
 UUID: Audio Sink (0000110b-0000-1000-8000-00805f9b34fb)
 UUID: A/V Remote Control (0000110e-0000-1000-8000-00805f9b34fb)
 UUID: Handsfree (0000111e-0000-1000-8000-00805f9b34fb)

When the device connects automatically (by powering on after being paired) A2DP is "unavailable".

To enable--and subsequently activate--the profile the device must be connected by explicitly giving the "connect 00:1F:82:28:93:51" command to bluetoothctl.