DIAGNOSIS That three-beep sequence is the saw telling you it’s in a safety lockout. It’s not broken, it’s just being overly cautious. The most common trigger is the chain brake being accidentally engaged.
FIX First, pull the front hand guard (the chain brake lever) all the way back toward the rear handle until you hear/feel a solid click. That disengages the brake. With the battery installed, try pulling the trigger. If it still beeps three times, double-check that the bar and chain are installed correctly and tightened—an improperly seated bar can trick the safety system.
IF THAT DIDN'T WORK The three-beep error can also be triggered by a communication fault between the battery and the tool. Pull the battery out, give the contacts on the saw and the battery a quick wipe with a dry cloth to remove any sawdust or debris, and re-seat it firmly. Try a different, fully charged M18 battery if you have one.
HEADS UP This lockout is a pain, but it’s there because the saw knows the chain brake is a physical, mechanical switch. If the brake is even slightly forward, the tool assumes you meant to engage it for safety, so it won’t let the motor spin. Just make sure you’re pulling that guard all the way back.