Hmmm, it would help if you posted a link of the url to inspect. I assume for privacy reasons your not looking to. I would suggest pasting the json content into myjson.com or something, and see if the Roku accepts that feed. It would help narrow down some things if it works or doesn't imho. If it does accept it, it's like something with where/how its hosted, or the url name & extension.
My next problem: I only have one video to display on my Roku Channel and it's an M3U8 live stream that isn't always running. How can I handle this situation? Right now the feed status returns:
Required video url is unreachable.
If someone views my channel when the stream isn't running, I just need to have a splash page with times when it is running.
Ok, on the json file problem on your server, You need to setup the mime type json to be handled as a script file and not a txt file,