The page is only a demo contact form (a reduced test case), so the only library that I’m using on that page is jQuery (2.1.3). I even used the source that Codepen uses for jQuery. I tried adding jQuery Mobile to the page because I had seen some posts over at Stack Overflow suggesting this, but it didn’t work so I removed it.
I can’t figure out why this is not working. It’s so frustrating!
Feel free to use Element Inspector on the page if that would help you.