Answer by Chris for Callback function is not executed

take

  $.ajax({       type: "POST",       url: action,       data: formData,       dataType: "html",       success: function(msg){        alert('23');       }     });

and add

error: function(error) { console.log("an error", error);}

using firebug.

it may submit correctly but not receive a valid response.

Using firebug you can watch the requests going to and coming back from the server to make sure your getting what you expect and that the status code is a 200 in the Net tab. Console.log will also output the response from the error in the console view.