Apple ID -> if everything fails...
I like to share my Apple ID trouble after migrating to a new iPhone...
I'm using 2 different Apple ID's (one is my main iCloud ID and the other is an older Apple Store account) and they got terribly mixed up. When logging in with my Apple Store account on my iPhone, it would actually login with my main iCloud account.
[BTW When logging in online at appleid.apple.com everything was normal and I could login to both accounts.]
Because of the mixup I could not download most of my apps. Or I would have to log out of my iCloud account, login on iCloud with the Apple Store account etc etc, and then still it would refuse to redownload all paid apps.
THE SOLUTION!
I went to iforgot.apple.com and clicked the I forgot my Apple ID link. Filled in my name etc and behold: my main Apple ID of my Apple Store account was changed to a different address!!!
I can now login with that address and download everything... and the funny thing is that it shows the old address as my Apple ID... How strange is that?!
SOLVED!