Make sure you select GrBL from machine profiles. Most surely http://you.have something missing in the gcode setup that’s not turning the the laser off. Also compare to the LaserWeb settings on the wiki
@Ariel_Yahni_UniKpty Thats what I’m running. It sticks an M4 S0 at the start of the code, tried editing the gcode setting to M3 and it does the same thing.