For some Bluetooth audio devices, you get this message:
"Device added successfully, but failed to connect"
I'm trying to setup A2DP Sink (Send Audio).

In /var/log/syslog, I get:

bluetoothd[692]: Unable to select SEP

basic Bluetooth command-line utils

List your Bluetooth devices:

And then show details about a specific device:

workaround #1

https://bugs.launchpad.net/ubuntu/+source/bluez/+bug/1199059/comments/13

This works for my Logitech receiver, but not my Homespot.

workaround #2

edit /etc/bluetooth/audio.conf

related bugs

And other related pages: