The RSS feed that I created for an Amazon Fire TV channels passes the validation. However, when I test it, I get an error saying that it cannot play. The feed is a video stream. I have set up the feed through a CDN. The stream works on Roku, VLC and through my iPhone. I am assuming that I must have neglected something in the "item" section of the feed, but cannot figure out what I am missing. Any assistance would be greatly appreciated. Below is the section of the code that I think is the problem.
<title>All Sports Television Network</title>
<pubDate>Mon, 08 Feb 2021 00:00:00 -0700</pubDate>
<description>All Sports Television broadcast feed</description>
<media:title type="plain">All Sports Television Network</media:title>
<media:description type="html">Linear television broadcast feed.</media:description>
<media:thumbnail url="https://www.astnetwork.net/images/All_Sports_Logo-1920x1080.png" />
<media:credit role="author" scheme="urn:ebu">Riki Smith</media:credit>