Hi @Jetah3,
Greetings from the Roku Community!
We're glad to assist you with your inquiry. Are you adding The Roku Channel: Britbox? Please be advised that there might be two separate apps for Britbox: one from the standalone channel and one from the Roku channel. Please make sure to download the correct app and ensure that the correct credentials are used. Kindly send us a photo of the app you are trying to add and the error message you are seeing if the issue persists.
Let us know how it goes.
Kind regards,
Eunice
Eunice L.
Roku Community Moderator