DIAGNOSIS A good battery with total silence points to a break in the start circuit. The usual suspects are the 30-amp main fuse blown, the start switch itself, or a safety interlock (like the oil sensor we talked about earlier) preventing engagement.
FIX Locate the 30-amp fuse. On the XP12000EH, it's usually in a small in-line fuse holder coming directly off the positive battery terminal. Check it visually or with a multimeter. If it's blown, replace it with an identical 30-amp ATC/ATO blade fuse. Also, ensure the battery terminals are tight and free of corrosion.
IF THAT DIDN'T WORK The next link is the start switch on the control panel. You can test it by using a jumper wire to briefly connect the two main terminals on the back of the switch (with the battery connected and in run). If the starter engages, the switch is bad. Also, double-check that the low oil alarm isn't activated and needing a reset, as that can disable start.
HEADS UP That main fuse often blows if someone tries to jump-start the generator battery while it's connected to the generator. Always disconnect the battery before using jumper cables or a battery charger.