Okay so I have the 4.4 version installed and I am trying to fly a leg from KPHL to KMCO. After starting the battery and going through the checklist, I start the APU. It does start and it gets to 100% but then after a few seconds, it shuts down. Also, even with a cold & dark cockpit, the engine sound is heard from an external view. When the APU starts there is no sound. Does anyone have any ideas as to why this happens?