Error previewing new app

I’m attempting to create an app to see if this is a feature we want to offer with our product. I have a test domain hosted within my cloudflare account. This domain is configured to serve a static html page from s3. I downloaded the sample app and changed the name per the instructions. I then went to the Developer Dashboard and uploaded the app. The preview window simply shows an error bar that says: " An error occurred loading this page. Please double check the URL. If it continues to fail, please try again later or contact support for assistance." and nothing else.

If I look in the developer console of my browser I see Failed to load resource: the server responded with a status of 503 ()

What can I do to move past this issue?

Today it just started working. That’s a bit frustrating but at least I can move forward now.