@dc42 The enable inputs can be set to accept high, low or any type of inputs up to 24v, so I don't think these are the problem. While troubleshooting I've set these to accept any but my plans was to use a spare pin and M42 command in the tool number for additional failsafe. The adapter seems to be very versatile and the manual suggests quite a few ways to set up.
That said I'm still having problems that feel like grounding issues with the heat terminals on the duex - I am using PWM-1 for the laser and E3-E6 to control LED lights through the deomon.g file.
I wired the ground from pin 4 on the CNC adapter to the laser PSU ground - separate from the stepper PSU. I had my signal go to inverted TTL from the Duet PWM 1 header. The controller turns on as normal, and if I press the red arm button and close the external switch (which I leave normally open at start-up because I use a key) the arm LED turns on but the Laser LED just flickers briefly on and turns off. What I've noticed also on the duet is E3 and E4 lights are on when only E4 should be on at start up. Those along with E5 and E6 for used for LED's which signal machine state. The LED for heater 2 does not turn on - it seems the pin is being pulled down or drained to ground - but if I open the external switch on the cnc adapter the LED for E2 lights up. The seems like like a ground issue.
In any case I have received some additional troubleshooting guidance from Opt Lasers which I will go over on the weekend to identify if it is the laser head or adapter.