A few months ago I set up A2DP with this tutorial.
After some time the Bluetooth seems to have stopped working. Not because of the tutorial, but rather because of software issues with the Pi.
Now, when I want to connect a Bluetooth device, the message "GDBus.Error:org.bluez.Error.Failed: Protocol not available. Try to connect manually" shows up. This wasn't the case before. As well, on my streaming device (Phone in this case) the options to pass over audio has disappeared, and I can only pair, but not connect.
I'm on Raspbian Stretch.