If you have a PRS or PRT Alpha, VN Switch #4 Stop Type should be Normally Closed. Is the physical E-Stop button reset (out), or pushed in? Rotate it to release it back to the out position. Sometimes dust, corrosion, etc. can cause the contacts inside the switch to not make contact. Take the cover off and blow it out, and also spray some contact cleaner in it and blow it out again. Put the cover back on and operate it several times. Check the indicator for input #4 on the screen to see if it toggles on/off. Make sure it's connected properly inside the control box (reference the manual for locations). Use a multimeter to check continuity in the cable.
Also, if you had to load the software on a new computer, make sure you used the right config file that matches your machine (PRS, PRT, Alpha, Standard).
Scott
"It’s easier to fool everyone than it is to convince them they've been fooled" - Mark Twain