Disney+ on AppleTV

You can use your existing Disney login details within the disney plus app on any device or Disney.com on a computer. You don’t need to use your Apple ID

https://whatsondisneyplus.com/disney-faq/how-to-watch-disney-plus/

The Disney+ app would have a sign up button for new subscribers (in-app), or a log in button for existing subscribers (from outside the app).

I don’t really recall how I went about it now. I did the free 7 day trial through my Apple TV, but before this I had a Disney.com account already and signed in with that. I later changed my account over at Disney.com to use my Apple ID, so I can’t test this for you now. I don’t remember why I changed it to my Apple ID

Its best to go into the Disney plus app directly, not via the tv app. Try it that way.

Or delete the Disney App and reinstall it, then try and ignore it suggesting the Apple ID, type in your Disney email.

Or see if changing your password over at Disney. com resets the login details, then test on Apple TV using the Disney plus app

Otherwise you will need to get in touch with Disney.

Many of the Apps you sign up for via Apple TV will not work on anything else and vice versa.

The Apple ID email would only be used if one was being billed through that account. If there is an issue with logging in using your other credentials then it would be best to contact Disney so they can investigate.