Katherine,
It sounds like you have one of a couple issues. . .
Most likely the panel is not asleep as the it would wake upon a momentary touch, per AMX
•Sleep: Only the backlight will be turned off after the user selectable time of inactivity has elapsed. Panel resumes the ON mode in ~ 1 second upon a momentary press of the touchscreen.
However, it very well could be in shutdown, per AMX
•Shutdown: Power to all peripherals and components is turned off. The system remains in this mode until either it is rebooted or the battery is completely drained. The panel is re-activated by pressing the touchscreen and holding until the AMX splash screen appears.
How old is it? as it may be a case of the backlight being dead as well. I’m up in Orange and have done work for the seagoing folks in Point Loma there, so if you need a set of eyes to look at it with you, I could do that for you as well.
Mark C