When I tried to watch Brit Box, I was notified that I needed to sign-in (I am signed in to Brit Box on my computer) so I clicked on Sign-in, but when the new screen came up and I clicked on Sign-in (to Brit Box) the Roku sign-in came up but it won't take my password and continues to say it is incorrect. I can watch our other streaming service without a problem (Acorn, PBS, etc.).
Were you able to ever get in? I just signed up for Britbox and same thing - it shows my email but when enter the password it refuses to recognize it. I then changed my password for Roku and tried again. Still doesn't work. Ready to cancel and try it on Prime.
Are you using the proper credentials? You should be using whatever email address and password you've established with BritBox and not your Roku account email and password.
I tried to sign in with both Roku email and password and Brit Box email and password. Neither is accepted. I have had uninterupted service for 2 years.
Are you located in US and subscribe/pay directly to Britbox? If so, go to the Britbox website https://www.britbox.com/us/ and try to sign-in there.
It is possible you might need to change your password if you haven't in awhile. Sometimes just selecting "forgot password" or "reset password" is all that is needed. (some services just lock you out with no message that a password reset is needed).