DIAGNOSIS The tool's field failure protection triggered. This happens if the motor overheats or the electronics sense a fault.
FIX Remove the battery. Let the tool cool down for 15-20 minutes. Reinstall the battery. It should reset and run.
IF THAT DIDN'T WORK The trigger switch or electronic controller might have failed. You'll need a service center to test and replace the switch module or controller board.
HEADS UP Don't try to bypass the protection. Repeated overheating can permanently damage the motor windings.