NCstudio, Y limit switch not working- do I need a pull up resistor?

Hello,
My neighbor has a machine from ld-cnc.com , it has been neglected for a few years, and am trying to make it work.
I have a problem witht he Y limit switch, ( X and Z are working fine) . the sensor used is SN04 and it is working fine, ( tested with a voltmeter) however the NCSutdio card is stuck on the high state ( limit switch is on) , so in order to work I have to reverse the polarity on the software, ( witch I assume is wrong , all am doing is forcing a down state on the limit switch so I can move the Y axis and I can't home the Y axis) .

Even when I disconnected the parallel port between the PC and the controller , the Y port remains up, ( X and Z go to down if they where triggered prior to the disconnection). I have read that I need to put pull up resistors, but don't' know what value to use. tried 330 and 2.2K with no success, however I will retry with better wiring.

the weird thing on the Y sensor input that it had 2 cables connected to it, I didn't trace from where the second cable is coming because I would have to dismantle the X gantry, so I disconnected it, am only connecting the cable coming for the SN04 sensor for the time being, but as I said even when the parallel cable is disconnected am getting a high Z state on the software.

all help is appreciated.

regards,