Cloyd,
I'm assuming you have the AGS unit with the dials running along the top of it (ME AGS). If so, the Ready LED (on your right as you look at unit) should be on. If not, turn the unit off, then enable it to reset it, per the manual. The Status LED (on your left) won't light until generator start has been attempted.
If you have the AGS unit that has no dials across the top of the unit (ME AGS-N) the Ready LED should be lit if if power is applied and the temp sensor is connected. If not connected the LED will flash. The Status LED will be Red or Green, depending on generator status.
I loaded the appropriate manuals to Coach Assist this AM.
Since you've verified that 12V is present, the only thoughts that come to mind is to verify that the 12V powering the AGS is from the same battery set as the generator start voltage. If that is OK it would seem you may have a faulty AGS unit. A call to Magnum 425-353-8833 would be my next step.
Steve