The navigational displays do not turn on even with APU on and APU GEN/ or External Power.  The ND's should be functional to review flight plans at the gate.  Currently the only
way to start the navigational displays is to start the engines using control E.  That is unrealistic.  Please make the Navigational displays turn on with APU or external power so we can review our flight plans before pushback.

In this picture the engines are running but the NDs are still not coming up.  you have to hit ctrl+E even after the engines are running and and the GENS are working.

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The aircraft is defaulting with an invisible "avionics master switch" in OFF, since it uses default systems. I understand that this may be addressed in a forthcoming update, but CS needs to confirm.

no idea if this is relevant to your problem, but I had similar issues until as part of an unrelated problem I found I still had the WorkingTitle G3000 addon on my system, and apparently it's not been needed since January. Removed it and many various issues I'd been having, including the displays in the 717, disappeared