Hi,
audio recorded on one 7k will play back on any 7k (or 2600).

You cannot just copy audio (eg using a pc) from the original sd card it was checked out to by Jukebox to another sd card, there is a copy protection system which uses the individual sd card identifier.

So why your card did not play is down to some other reason. Different firmwares? inability to fully recognise your sd card? fault on his 7k?