What should I do if my MJ401E Lawn Mower has stopped working? If you find that your MJ401E unit does not start, find the unit's rectangular reset button located near the safety start button. After doing this, start your lawn mower as usual. Related articles I've pressed the switch button, then squeezed the handle, but my Mow Joe MJ401E does not power on. What should I do? Where can I find replacement parts for the Sun Joe Mow Joe MJ401E Lawn Mower? My unit is not starting. Lawn Mower Troubleshooting Battery and Unit Compatibility Guide