I have a relative who smashed their iPad beyond repair. It's been replaced with a refurbished one. I restored the tablet from a backup on my computer (Win7, if that's relevant). It boots properly and the expected wallpaper and apps from the old machine are present.
However we can't login to iCloud on the device. It always says incorrect password. To troubleshoot we logged in to iCloud on my computer, being very attentive to the email and password spelling. It worked.
The password is a dozen characters, mixed case alpha numeric (no symbols or punctuation). I'm absolutely positive it's being typed correctly.
Why is the correct password on iPad being denied?