A PLC instrcution for a Normally Open STOP button (if one existed) would be an XIO and look similar to a NC contact, but a PLC instruciton for a typical Normally Closed STOP pushbutton looks like the XIC instruction (an open contact). In other words, you use the opposite-appearing instruction for both cases (if anyone did ever mistakenly use a real N.O. STOP button).
First, you need to make a big adjustment in your thinking. The Input instructions in your ladder logic do not and were never meant to represent the actual appearance of the physical device that is sending the input. They only represent how YOU want the program to interpret the signal from the physical device. Once you adjust your thinking like this:
"The PLC input instruction XIO does NOT a produce a copy or clone of the state of the physical device", but rather its inverse.
Then you will not have any more problems with this part. You can do a site Advanced Search look back at old posts. That topic has been discussed on this site too many times to count, and probably will be talked about here forever, as long as PLCs exist in their current form.
If your simulation software allows you to use a XIO for a STOP pushbutton, then it has a severe error in its program! I would think twice about this software, if indeed that is the way it is. Does your simulation software also allow you to set the type of physical pushbutton? If so, perhaps you do not have your physical button set up to have a normally closed (N.C.) momentary contact. Stop and Emergency Stop buttons should have NC contacts, while Start buttons should have NO contacts.
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