Cannot get date to auto-populate to today's date like I did on other documents before

I did a search a while back for how to get the date to autopopulate to today's date. I found an article that gave me this javascript to use (I do know know anything about java script so this was completely new).

This is the script: var f = this.getField("Today's Date");f.value = util.printd("mmm d, yyyy", new Date());

I created a text field, labled it "Today's Date". Clicked on the Javascript tool, then on Document Javascripts, names the script "Today's Date" and then put in the script and it worked.

I am copied and pasted that script and followed the same process for other documents and it has always worked.

Not now, I am trying to do the same and it's not working.

I tried clicking on Debugger just to see what that was (I have no idea what I'm doing) and this is what it showed:

Can someone help please? I would sure appreciate it!