Error Opening up my new project in the prototyping phase

When opening up of the given app it just keeps of loading 2 specific files when inspected on the browser. One of them gives a status code of 502(Bad Gateway) and the other gives 404(Not Found)

If any one could please help me go through it, it would be really great, because this project will have no real value after a few days, and they’ll reply after monday.