Try another output pin. There should be plenty. I have heard of PC's with faulty pin 1's - which was a strobe pin, whatever that was.
You can use any available output pin - 2 - 9, 14,16 and 17. I actually use pins 8,9 for my M3 and M4 . The same applies however - Config/Ports and Pins/Spindle Setup - untick disable spndle relays, and select an output number.
Config/Ports and Pins/Output Signals - allocate the output to the pin of your choice.
If you are set up and you do M3 command, you can check the breakout board and see if the signal changes. M5 turns it off.