If you've already restarted your Roku and it hasn't helped, generally when a problem is confined to one channel/app, the first thing to try is to remove the channel (highlight it on the Home Screen, press * on your remote, choose "Remove channel"), restart your device from Settings->System or Settings->System-Power (as appropriate), add the channel again from Streaming Channels. Don't skip the restart step or do it out of order. The remove, restart, add procedure doesn't always fix issues, but it's a good place to start.
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