Apple ID not valid or supported
I changed my email address for my Apple ID on one device before signing out of another device and now I cannot use my iPad.
iPad Pro 10.5-inch, Wi-Fi
Why can't you use your iPad? Can you sign out of the ID and then sign back in with the new version of the ID? If not, what happens when you try? Error message(s)? More information would help.
See the article below.
What to do after you change your Apple ID or password - Apple Support.