My mower is not starting up. What are some potential issues? Issue Possible Cause Mower fails to start The safety key may not be inserted The motor/blade control is disengaged The battery may be faulty or flat The mower deck is clogged with grass or debris The grass is too tall Related articles My unit is not starting. What if I need to service my Sun Joe Mow Joe Lawn Mower? What should I do if my MJ401E Lawn Mower has stopped working? Why Isn't my unit turning on? How do I start my Power Joe?