jQuery AJAX Post not posting data

Try changing the contentType to application/x-www-form-urlencoded or just dropping it since it is the default value.

Your problem is that the data you are posting is not matching the content-type you are sending.

contentType is for the data being sent to the server, and dataType is for the data being received from the server.

Just remove the contentType: "application/json" from your code.