CheckBox Jquery - Prompt Not Working

I had this working previously but for some reason it has stopped working, a syntax error I presume. Can anyone spot the issue?

I have had it running with the html inserted into the source on a browser and Jquery in a console. But not in JSFiddle and a few other options.

It should prompt when ticked and prompt again if unticked:

<td class="icon">
            <input type="checkbox" id="my_checkbox">
    </td>


    $("#my_checkbox").click(function() {
      if (this.checked) {
        this.checked = confirm('Are you sure you want to CONFIRM the order and EMAIL THE CUSTOMER?'); 
      }    
      else {
        this.checked = !confirm('Do you really want to change this to NOT RECEIVED?'); 
      }  
    });

http://ift.tt/2eJckEq