I cannot engage the autopilot

[Debowing]

All is operational but my AP just won't engage

[Coop]

There are a few requirements for AP to be able to engage:

• The "Turn" knob must be centered on the AP control panel on the center pedestal. There is a clickspot on the knob that will center it for you as well.
• The attitude gyro must not be in fast erect mode. This is the lower left switch on the pilot's switch panel located to the left of the main pilot's displays
• The ATT2 gyro must not be enabled as the EADI source. This is the button underneath the DME power button on the pilot's panel. "ATT2" would show on the EADI if it is selected. 
• The ATT1 gyro must be aligned. (If you see the horizon bars on the EADI, it is aligned)

[Debowing]

Thanks - the problem source was the turn knob, it was slightly not centered...