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.
Try removing the channel (highlight it on the home screen and press the * button on the remote - choose "Remove channel"), restart your Roku (from the main menu "Settings->System->System restart" or just unplug the power for a few seconds and plug it back in), then add the channel again from Streaming Channels. Don't skip the restart step. Just removing a channel and immediately adding it back doesn't accomplish anything.
Once it's added back see if you can then sign in again.