Free Flightdeckmag wrote on Sep 6^th, 2015 at 5:30pm:

No. 1. Start FSX 2. Load B721-200 3. Battery On, Galley Power On ... (3D Panel) 4. No com or nav available at 3D-Panel Can only change them if use Ctr E before.

It would appear your Avionics Master is off. There's no switch for it so you'll need to create a keyboard short-cut.

Select the menu 'Options', 'Settings' then 'Controls'. Choose the 'Button/Keys' tab.

Scroll down the 'Assignment list' and select 'Avionics master (on/off)'. Now select the 'New Assignment' or 'Change Assignment' button.

In the dialog box, select the keyboard combination to use, i.e. Ctrl + Shift + A, then select the 'OK' button.