So, I'm trying to watch Disney+. I have a subscription. Good for 5 more months. When I try watching the channel, it tells me to login. I try to login. It says to use my email for Roku account. I continue with the email. It says "we couldn't find an account for that email".
Are you sure it's telling you to use your Roku account email or just asking you if you'd like to use it?
Ditto to what @renojim said.
I use a different email address for my Roku account than I do for most everything else. When I go to log on to a channel it asks if I want to use my Roku email address and I have to tell it NO, so that I can then enter the needed address.