Apple TV app login fails with extra 'S' in email

Trying to help sister watch Apple TV on Samsung TV UN43NU6900. Installed app, it requires login to Apple account, but the User ID is pre-filled with email address, but has an "S" after the .com; this is preventing the app from recognizing the account as valid.

I can't figure out where this is being pulled from, so I can delete the "S".

Anybody have experience with this?

Thanks in advance!

Rob C.