To fix Netflix on your Roku, try a system restart first: Settings > System > Power > System restart. If it's still broken, you can try removing the Netflix app and reinstalling it. For that, highlight the Netflix app, press the star (*) button, choose Remove channel, restart your device, and then get Netflix back from the Channel Store. If nothing else works, physically unplug your Roku and TV from the power outlet for 60 seconds to perform a hard reset.