DIAGNOSIS Almost always a battery communication or terminal issue. The tool isn't getting power, which points to the battery connection or a dead cell in the pack.
FIX Start with the battery. Reseat it firmly. If that does nothing, try a different, known-good Makita 18V LXT battery. If it works with the second battery, the first one is likely the problem—check its charge indicator.
IF THAT DIDN'T WORK Check the battery terminals on the tool and the battery itself for dirt, debris, or damage. Clean them with a dry cloth or compressed air. Bent or corroded terminals will break the connection.
HEADS UP If multiple good batteries don't work, the tool's internal electronics or trigger may have failed. This isn't a user-serviceable fix and requires a service center.