I changed my Apple ID to a new email address because the old address stopped working. However, the App Store still wants my old address and the old ID (email address) and password are invalid. How can I fix this?
MacBook Pro (Retina, 13-inch, Mid 2014), OS X Yosemite (10.10.2)
iTunes and Mac App STore purchases are forever registered to the Apple ID that bought them. Apple does not transfer purchases from one Apple ID to another Apple ID. Apple does not merge Apple ID accounts. The Apple ID is encoded into the licensed copy that you downloaded to your Mac and that is the only Apple ID that can redownload or update the purchases.
You erred making a new Apple ID. You should have simply changed the primary email address associated with the Apple ID.
Changing the email address you use for your Apple ID -
http://support.apple.com/kb/HT5621
It is too late to do that now because you have used your email address to create the new Apple ID. An email address can only be associated with one Apple ID.
There is a very complicated process to reuse the new email address.
Changed Apple ID, but app store still wants old one
