I have this same problem today, and none of the proposed solutions worked.This is my own computer, so I am the system administrator. I only have one Apple account. I removed the SC Info folder and restarted. I've logged off and logged back on. I still get the message "This computer is no longer authorized for apps etc." When I click on Authorize, it still responds with "This computer is already authorized." Any other suggestions?
I have that same problem. I just migrated my old computer to my new one, and cleaned up my old computer to give to my grandson.
When I plug in my iPad, it wants to upgrade my IOS, but I get this authorization loop, with these two screens:
This Computer is already authorized.
Including this one, you have authorized 5 computers out of your available 5.
This computer is no longer authorized to play purchased items
that are on the iPad “iPadHoward Brazee’s)”. Would you like to
authorize this computer for items purchased from the iTunes
If you do not authorize this computer, 6 songs, including “House of the Rising
Sun”, will be removed from the iPad