Bluetooth pairs with headphones, but cannot connect to Audio Sink

Xubuntu 17.10 on Dell Inspiron 17 5000 series laptop. Atheros 0cf3:e009 Bluetooth adaptor, officially certified by Ubuntu.
Bluetooth works. I have paired with my phone, and can transfer files.
I can also pair with my headphones, but every time I try to connect to Audio Sink I receive this error message -
"connection Failed: blueman.bluez.errors.DBusFailedError: Resource temporarily unavailable..."
Pulse audio works, and I have the Bluethooth modules installed. These headphones have worked with another laptop running Xubuntu, and work now with my Android phone. What could be the problem?

Ubunutututu Knock Off -> Ubuntututu issue

Bluetooth not working in Ubuntu 16.04 with [0cf3:3004] Atheros adapter

google fun ..

https://cateee.net/lkddb/web-lkddb/BT_HCIBTUSB.html

I do not know if this bug has been fixed. best to check into it yourself.

OK, I already read that old post, and every other on the Ubuntu forums which sound possibly relevant. Different version of Ubuntu, and also a different model of Atheros adaptor. My Bluetooth DOES work. I can pair devices, and send files with it. I just cannot make it connect to Audio Sink. I get this Dbus error all the time. I do have the Bluetooth discovery module in pulse audio (an older problem, much discussed on forums,which I have fixed before on another machine). This is something else, and has me totally beat.

is this bt device a head set or ear piece? either way if it is telling you it is NOT in discovery mode, so then put it in discovery mode so it will pair up to it then connect. did you try that yet?

As stated in my original post, it is a headphone set. And it was discovered and has paired with my Bluetooth adaptor without any problem. During set-up with Blueman it was reported as paired, but failed to connect. It is therefore not connecting to pulsaudio and of course cannot receive anything. When I try to connect it manually To "Audio Sink" I get that Dbus error, and that's all.
I had a very similar error with my old laptop, which was fixed by installing the pulsaudio bluetooth-discovery module and loading it. But with this computer I already have that module loaded, and it still does not work.

I ran - $ systemctl status bluetooth, and the log contains this for each connection attempt:-
"Unable to get connect data for Headset Voice gateway: getpeername: Transport endpoint is not connected"
That is massively unhelpful to me. What does it mean?

I do not know, what I do know it every time I go to hook up my BT headset/earbud thingy, I usually have to fiddle with it connect - reconnect, delete the thing in blueman reestablish pair hook up to it again. until I get it to work. so I have no one time solution fix all. sorry.