Can not start so my diesel

My 2-liter diesel (Passat 3C, BJ 2007) has a fresh battery in it, but like to go empty when the car is a few weeks. But it's still enough juice in it that the doors open and the indicators. Nevertheless, no start possible with the Bully Powerpack, although it indicates full power (green LED).

I have now been twice and each time the pack no start was crowded, but possible. So loaded battery and everything went back. So bring me the whole thing but unfortunately nothing.