In an attempt to CHECKIN or LABEL a volume it was discovered that the volume's true WORM characteristic didn't match that described by its barcode label.
The volume is not checked in.
The volume was probably mislabeled. Find the volume in the library. Simply remove the volume, or swap the barcode label with a label of the opposite WORM characteristic (WORM for non-WORM or vice versa) and retry the check in command.