Read all this before taking any of the steps.
First, verify the email address for the Roku account under which the device is listed. Settings > System > About
Is that the email address you expect? If not, then you'll want to factory reset the device and re-register the device.
If that is the email address you expect, go to https://my.roku.com and log in (same email address) and go to the Manage your subscriptions link. Is there one for Disney Plus? I would expect not, but if so, this indicates something else entirely going on that should be resolved.
If there is no Disney Plus account listed there, remove the Disney Plus app. Then reboot the Roku, as well as any other Roku devices you have. Then reinstall the app.
You should be able to log in with your Disney Plus subscription.
Oh, by the way, Disney isn't supporting Disney Plus With Ads on Roku. Don't know why, but if your subscription is the With Ads version, you can't use that subscription on Roku, until Disney decides to support Roku for that version of the service.
Roku Community Streaming Expert
Note: I am not a Roku employee.
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