Don't use the 2d radio panel. It appears to freeze the ground power switch on the engineers panel. Use 3d on the console. See if that helps.

Shut down FSX and restart it and the problem goes away, as long as you don't use the 2d radio. You can shift2 BA EP and go to backup power plus have radios.

Edit:
Last night I was switching between the 737 and 727. That must of screwed something up with the gauges. Today I loaded only the 727 and the radios work regardless of ac power, ground power, or battery on or off. 3d only, never use 2d.