Using an old Sky+ Box, recordings not playing

Hi

Please bear with me, a friend of mine has the following problem

Firstly he had a Sky+ HD box in his previous address, which he cancelled when he left, and kept the old box.

Bought a new house and got Sky along with multiroom - 2 new boxes

I suggested that he should replace his multiroom box with his old Sky+ box so he can pause, rewind, rec in both rooms

He put his new multiroom card (red) into the Sky+ HD box and got it paired by Sky, and now has Sky+ in both rooms

But I thought he could watch his old recordings from the previous address - but he's getting a playback error message

Any advice

Thanks