Hello,
I took some days off during Christmas period 
That is really a bit strange.
Regarding the Broker, you first need to either install a separate Broker (see [OH3] MQTT Setup and Configuration for details).
Then you need to put either 127.0.0.1 (if the broker and the geckoclient is on the same machine) or the IP of the machine the broker is running on else and depending if you have setup a user and password the values.
But that should not be a problem. At least the client should start, the log file should be created and something should be logged in there. Do you see anything inside when starting the client from the command line?
Best regards
Frank