Check if the DDS4 is insert in file /usr/sam/lib/C/pd_devinfo.tx if not insert following lines (example for a C5687A, replace it with your model):
TAPE:::stape::::.*C5687A.*:::::::C5687A 40 GB DDS Data Compression Tape Drive (DAT40E):BR,DAT
There is no good troubleshooting with bad data