Associated AppleID and iTunes
I just bought a movie through iTunes (and I have rented and bought several movies before using the same iBook). Today, when I want to watch the movie I just bought, I get a message saying "This computer is already associated with an AppleID. You cannot associate this computer with a different Apple ID in XX days."
Why does this happen? I haven't changed Apple ID on the computer in many months, and I can see in iCloud that the right ID is the one in use.
Thanks, any help much appreciated.
MacBook Pro (Retina, 13-inch,Early 2015), macOS Sierra (10.12.6)