Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
I did a search on the Roku web site for anomalies, and it returned nothing. If it was a private channel, it might have been removed. There's no guarantee a private channel will always be available. If it was a public channel (found in the store), it might have been reported for streaming copyrighted material without permission. That too would cause it to be yanked. Roku has gotten very sensitive about that, because of lawsuits in other countries. And you can't blame them. If a channel is not meeting the required standards (and having permission to stream the video is a big one), then it will disappear.
Dan Nvidia Shield, Roku Stick (3600), Ultra (4640), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.