The way this set up works is this:
The part number 0G0627 is the voltage sense transformer.
240V is fed to the transformer from the utility grid. This 240V is converted to 16VDC and fed to the control board.
As long as the control board sees this 16V, it knows there is power in the grid. When this 16V reference signal is lost, it knows that grid power has been lost and starts the set.
Since you have already measured voltage at N1 and N2 (it should be 240V), we can easily test the rest of the system to find the bad component.
Open the control panel to expose the main control board.
Find the wire number 224 connected to pin number 10 of the board.
Find wire number 225 connected to pin number 17 of the board.
Set your meter to VDC and connect the leads across these 2 wires.
If 16VDC is not measured, the transformer is bad.
If 16VDC is measured, the control board is bad.
Just in case you are curious, the other 2 wires coming out of the transformer, wires 224a and 225a, are the battery charge wires. The transformer also serves as a trickle charger for the battery when the set is not running.