Transport-error / Unknown ERROR

Having a lot of trouble specifying the Direct Publisher Feed URL.  No matter what I submit I get the following error on the Video Format field

"There was a transport-level error - (Unknown ERROR)."

I can access the feed publicly at S3 and I am specifying the Video Format as "Specified in feed (Roku Feed Format only)"

I have validated the JSON (it is a valid JSON format) and I can;t see any keys or values that are not correct according to the spec on GitHub.  

I'm wondering how in the world there can be such a meaningless error message?  How do people get things published?

Here is my simplistic feed I am playing around with

{
  "providerName": "Testing Feed",
  "lastUpdated": "2018-10-31T21:01:46.035Z",
  "language": "en",
  "categories": [
    "Latest",
    "Category One",
    "Category Two",
    "Category Three"
  ],
  "shortFormVideos": [
    {
      "id": "m20181029190332",
      "title": "The Workshop: Jump Rope - Drilling the Rope Swing ",
      "releaseDate": "2018-10-29T22:00:00+00:00",
      "content": {
        "dateAdded": "2018-10-29T22:00:00+00:00",
        "videos": [
          {
            "url": "https://d3l7mm4198npa8.cloudfront.net/free/180927_buddylee_coordinatingtheperfectjump/180927_buddylee_coordinatingtheperfectjump-1080p.mp4",
            "quality": "FHD",
            "videoType": "MP4"
          }
        ],
        "duration": 148
      },
      "thumbnail": "https://d1s2fu91rxnpt4.cloudfront.net/mainsite/m20181029190332/display/BuddyLee_Coordinating_WEB.jpg",
      "shortDescription": "\"We're trying to coordinate the rope swing with the perfect jump.\" ",
      "tags": [
        "instruction",
        "jump rope",
        "buddy lee",
        "specialty course",
        "Latest"
      ]
    }
  ]
}

Any pointers at all would be greatly appreciated