Updating id and password on mini ipad for accessing iTunes

Because I changed my email address, I changed my Apple ID and password recently on my MAC desktop and iPhone 6 Plus but my mini iPad does not accept the new information. When the iTunes sign in box appears and I enter my new id and PW, it says it is incorrect. When I put in the old id and PW it also says it is incorrect. This is preventing me from purchasing or being able to updates my apps on this device.

Any suggestions?