Ok, this is a unit that I am not certified on.
I will try to help you if you want me to, or I can opt out and see if someone else wants to take over. Just let me know.
If you wish me to help, the first thing we need to do is to establish if the problem is actually in the genset, or somewhere else.
Open the control panel to access the back of the main circuit breakers.
Note that the supply wires to the circuit breakers are wires 11 and 44. Also locate the neutral bus, which has wires 22 and 33.
Turn the main circuit breakers off.
Set your meter to ACV.
Start the unit manually, and test the voltage from 11 to neutral, and 44 to neutral.
Both should read about 120VAC. If they do, the problem is not in the genset.
If they do not, the problem is in the genset.
If the problem is not in the genset, I need to know which transfer switch you have
If the problem is in the genset, shut the unit down.
Locate Terminal Block 1 (TB1). It is the terminal block with 2 rows of 12 screws. Note that one side of the block is labeled A, and the other side is labeled B.
Remove wires 1 and 4 from TB1, screws 2A and 3A.
Wire 1 is ground, and wire 4 is positive.
Make up 2 jumper wires that you can connect to wires 1 and 4, putting a 3A or 5A (no higher) fuse in one of the jumpers.
Connect the fused jumper to wire 4. Connect the non-fused jumper to wire 1, and the other end to ground.
Set your meter to ACV again.
Connect the other end of the fused jumper to a good 12V source, and start the genset.
Check the voltage at 11 and 44 again.
Let me know what you find.
This will tell us which end of the generator the problem is in.