If you paste commented string into browser’s address bar - it will work just fine.
I also tried hurl.it and jQuery AJAX Code Builder - both working OK. Yet codepen.io logging obscure error object into console.
You can open your chrome developer tools to view your errors. You have done this correctly just visit your CodePen on http instead of https http://codepen.io/O_Prime/pen/rybWwa/ . The extra security is stopping the unsecured request as OpenWeatherAPI is http.