Hi,
section 3.1 page2 shows a representative circuit diagram of an input pin. Note the that input has a 220Ohm resistor and a LED to ground. You will require
a input able to source 20mA in order to be sure that the input is genuinely logic high. Your normally open switch will have to be CLOSED in order to pull the input
pin high. Is this what you intended? To Estop Mach you would have the switch contacts open.......
Make sure your choice of source for the 5V for your Estop switch is correct and can source sufficient current. Do you have a multimeter?
If so measure the voltage at the 5V source and then again at the input pin with the switch closed, it should be 4.1V or more.
Craig