I can't use my Apple ID on my iPod 5th Gen
Some time ago I changed my Apple ID for my iPad. However, my iPod keeps asking me to sign in but on my previous Apple ID. I can't change the old email it is using, and it doesn't recognise either my old password or my new one. I still works, but I can't download any apps (even ones I bought previously) and the box asking me to sign in keeps popping up all the time. I have tried to connect to iTunes but it says there is an unrecognised iPod and I need to sign in - which I can't do! How can I sort this out?
[Re-Titled by Moderator]