Problems signing into Apple ID-nothing happens
My dad's email was hacked recently so he changed the email associated with his Apple account. He was able to change his log in on his iPad without any problems but nothing I've tried will work for his iPhone (4s; iOs 7.0.4). I've gone to the iTunes & Apps tab under Settings to log into a new account, but nothing will happen. I've entered his information-and tried my own account once- but after cliking "sign in" it loads for a bit, the info is grayed out like it's loading, but after a few seconds it just stops and won't sign in. I've tried resetting as well as a hard reset, I've closed all the apps running in the background, I went to downlaod an app to see if it worked after all, but it still prompts a sign in with his old email, and wont accept the password. Any ideas why this is happening/how I can fix it?
iPhone 4S, iOS 7.0.4