AMF Type NC3, SEG Woodward

I have a trouble on the goods above, that at the front Mimic the main voltage available LED is not ON although the terminal A1,A2, A3 are measured good.

Eventually it can't be set on Automatic mode, because the controller detect no voltage in main line then auto switch to GenSet. So I state the AMF in Manual mode.

Is there anyone here have ever experienced the same problem? or please anyone help me find out what's actually going on and how to figure it out?

thanks, guys.