Why Isn't my unit turning on? The unit comes with a safety feature, where the unit will not turn on if the battery is not inserted correctly. Related articles What should I do if my MJ401E Lawn Mower has stopped working? How do I assemble my MJ401E-PRO? Is my 24V battery compatible with this unit? A My SJH904E Hedge Trimmer isn't operating properly, what do I do? Is there a quicker charger available for charging my battery?