Desktop Controller doesn't connect to Sonos anymore

I'm having a strange problem right now: the Desktop Controller (on Mac) isn't able to connect to my Sonos system anymore.

I did have a Bridge and Play at my parents home over the weekend but did reconnect them to my home network now.

Some observations:
- Sonos Controller on iPad connects fine
- From my Mac I can access the /status page of a player.
- My own App on the iPad simulator directly on the Mac also connects without problems and shows all players.

Thus I don't think that there are network problems of any kind and also the Bridge properly connects to my Play's via SonosNet?

I did restart the Mac now, in the Sonos Desktop Controller selected "Reset".
So right now it says "Welcome" and on the next screen asks me to hold when I start the Sonos Controller it says I should press the hardware keys to trigger the detection. I do that, the lights start blinking as usual.
But nothing changes in the Desktop Controller, it times out after two minutes :(

Anything that I can do to better troubleshoot the problem?
Or is there some other way to restart/reset the Desktop Controller, so that I can start from scratch?