Don't worry I managed to find my problem.
The trick was to activate the logging in the m2ee.yaml file:
#example of file logging by the platform itself name: FileSubscriber type: file autosubscribe: INFO filename: /home/jfm/mxlog.txt maxsize: 10485760 # bytes(!!) maxrotation: 7
Though you shouldn't place the log file here, it was useful for quickly debugging the problem.
As it turned out I hadn't activated TCP/IP connections for postgresql :)