json is a text file to pass information between applications. It usually passed to and from javascript but can be used for a lot of different purposes. A good place to start debugging is in the console of your browser. The console will display any javascript errors that have occurred. If you are in Chrome you can right click on the page and select the option inspect. You should see a series of of tabs come up. It usually displayed on the bottom or the right hand side of your screen.
The json file probably didn’t build correctly for some reason. If you are doing anything with REST it could produce the error also. REST passes data by using JSON files as well.
Most of the time there will be an error in the console that will give you an ideal as to what is causing the problem.
