GRBL Fire Button

Hello again
If your laser has 3 Pins (GND, V +, TTL) this can be controlled by pwm. The 3rd pin that is not Power, should be the PWM control. This pin must not be left open or without connection, it must go to GND to not activate the laser and + 5V to activate it.
Try to energize the laser with 12V and the 3rd pin (if it exists) to GND … if it does not fire, it is a good signal.