I created a published feature layer from a geojson file. The creation succeeded, but when the creation completed, and the browser navigated to the site for the published feature layer, a generic error message was displayed.
After I modified my code to add the layer to a map, it failed with error Invalid URL. The URL that I put in the code was the URL from the published feature layer site, with /0 appended. I'm not sure how to fix the problem, since no error details are given.