DIAGNOSIS The control board is getting power (Ready light on), but the inverter circuit is not delivering AC. A tripped or faulty GFCI outlet is the first check.
FIX Locate the 120V 20A duplex outlet. In the center is a GFCI reset button. Press it in. You should hear a click. Test with a known-working lamp or tool. If it trips again immediately, the connected device has a ground fault.
IF THAT DIDN'T WORK The issue may be the DC side. Check the 15A DC fuse on the control board. It is a standard automotive blade fuse. Remove it and inspect the filament. Replace if blown with an identical 15A ATC fuse.
HEADS UP The GFCI on this model is sensitive. It will trip if you try to use it with an extension cord that has a broken ground wire. Always test the generator outlet directly with a simple load first.