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 from the Roku home screen by navigating to the channel tile, pressing the * key on your remote and choosing 'Remove channel'. Then restart your device from Settings>System>System restart. Once your player starts up again, add the channel back once more.
Does this clear up the issue you are seeing? Please keep us posted.
Please note that if you are removing a subscription channel billed to your Roku account, you must cancel the subscription first before you see the Remove channel option. You can check this link for step-by-step instructions on how to remove then re-install a channel: How do I resolve channel playback issues?
If the issue persists after the suggested troubleshooting by @RokuDanny-R, we suggest contacting BritBox support to report the issue and for further help. Channel logins and authentication are solely handled by the channel developer.