You’ll need to provide the user_login parameter in your JSON URL, in addition to migrating to the New API. In my case, I had to provide the user_id, but try that. All the info on optional parameters are in the API Reference page, like @Dist mentioned.
But to give you a bit of an edge, you’ll need to check if said stream is live. If it is, you’ll need to check its data and if it exists. If it DOES, then you can change the classes from your divs and execute the rest of your function.