Could not retrieve the CDN endpoints in subscription with ID
This isn't really a direct answer, but could help with the general problem of "what happens if the CDN goes down?". There is a recent development called the "Progressive Web App".
Basically unless served by localhost, everything has to be over https, but script is cached as a local application in your browser.
When your app makes requests to the registered domain, these are intercepted by a callback you put in your serviceWorker.js, so you can cache even application data locally, and sync the local data occasionally with the server (or on receive events if you're using webSockets).
Since the Service Worker intercepts REST calls to the registered domain, this in theory makes it fairly easy to add to just about any framework.
https://developers.google.com/web/fundamentals/getting-started/codelabs/your-first-pwapp/
Sometimes there is a (global) problem with the CDN. It happend before.
You can check the azure CDN status on this page: https://azure.microsoft.com/en-us/status/
At this moment everything looks good, you still have problems?