Based on the example you have given below your question, the problem is that there is no element with a class of now-playing
.
Your page seems to have been cut short, perhaps due to an error, but the ajax request fires and in the console I can see the response (the url is actually echoed before that as well):
I am currently listening to 01. Circles Around The Sun by Dispatch on Spotify.
Adding a <div class="now-playing"></div>
should do the trick.
Edit: Note that your key is visible in the response as you are echoing the url you are making a request to. It might be a good idea to change the key when you have solved your problem.