A weak battery can do this also, it may have enough juice to start the bike but not enough to make it shift. try rocking it back and forth also, somtimes they get stuck in gear. Can you hear a click like it is trying to shift but just wont or is there nothing at all? there could be dirt in the shift buttons or a wire unplugged.... there is a few things that can happen with the ES, luckily I havent found any major ones myself YET! Does the shift indicator on the dash pod have an N or does it have 2 dashes -- , is anything blinking on the pod? I would start with the basics and try charging the battery if the display is not blinking anything.