You wouldn't have been able to copy anything to the disk if it hadn't already been formatted. So something has gone wrong during or after the copying. You either have a faulty floppy disk, or one of your drives is faulty. It might be as simple as them needing a clean, but it has been along time since I've seen any floppy drive cleaners, with the format becoming more and more obsolete. If you can get hold of some, try that first.
I presume you still have the original data somewhere?