I have the exact same problem.
I tried running device-client -v to see what was going on and it seems like my device does not event have a key.
Starting device client
Starting listening...
Sending request to 'ds.onion.io/qwqw/listen?key=qwqw'
Write_callback: received '23' bytes, time: 'Wed Jul 12 15:14:12 2017
'Write_callback: valid json: '{"error":"auth failed"}'
error : "auth failed"Completed GET
Connection lost!
Restarting connection (restart #102) ...
RESPONSE THREAD!
Sending POST to url: '', post data: '{"error":"Could not find 'command' object!
"}'POST Sent! (url: '')
Error: ErrorClosing RESPONSE THREAD
Starting device client