The library barcode reader is unable to read the label of a tape cartridge. The cartridge is found in the slot with the given element number.
The cartridge is loaded into a drive and its label will be read from the tape.
Cancel the process if you do not want to load any cartridges into the library's drives. Examine the cartridge to ensure it has a barcode label and that it is compatible with the barcode reader. Not all vendors' labels are readable by all libraries. Check that the barcode reader is configured and is functioning properly, if necessary.