It looks like you're trying to use a feed file from another system (Apple TV?) to create your channel. As such, the feed file does not conform to the Roku MRSS spec. Take a look at some of the samples on the forum, or the Roku documentation.
Public Roku Channel: Rowing
Windows software for creating and managing MRSS, JSON, and FireTV feeds @ https://www.rokurowingchannel.com. No Programming, JSON or MRSS knowledge required.