Apple ID locked on one device

Greetings. I have an iPad3 and an iPhone 7. My apple id and password work just fine on my iPhone and via iTunes and apple.com on my PC. But my iPad will not accept the same password for the same apple ID. I keep getting prompts on the iPad to enter my apple id and password and when I do I get a message that my account is locked (it's not locked on any other device). I've tried unlocking it via the code sent to my phone, etc., and it keeps prompting me to change my password. I've done as well and updated the passwords on my iPhone and PC. I've tried signing out of iTunes and iCloud on my iPad but it requires you to enter your current password to do that, and it won't accept that password. I've gone so far as trying to completely erase and reset my iPad but .... it requires a password to do that!! Please help. I can't download or update any app or do much of anything. Thanks.