jQuery read content in external html file inside project

In my iframe.html, I have "select element" and when it change, it will call my javascript function which read content from external html file, located at assets/template/xxx.html, using command $.get("path_to_file", callback(){}) . 

When I test on my local, the program run properly but when I deploy to server it get error below:

https://521412.apps.zdusercontent.com/521412/assets/templates/xxx.html 403

Please suggest

Thanks