I have just rebooted the server (MA server is the Cell Manager itself) and double checked the configuration and it is correct.
DP debug.log file reports:
2016-01-11 10:55:55.833 BMA.596.2324 ["/ma/spt/sctl_NT.c $Rev: 50629 $ $Date:: 2015-11-01 01:29:17":1804] A.09.00 b105
SCSI_NT_CMD: RETURN: ERROR (GetLastError()=87)
scsiret - -1, eom - 0, key - 8, code - 0, qualifier - 5, flags - 38
2016-01-11 10:55:55.835 BMA.596.2324 ["/ma/spt/sctl_NT.c $Rev: 50629 $ $Date:: 2015-11-01 01:29:17":2387] A.09.00 b105
SCTL_Write: (scsi addr=4:0:8:0) error. [1026] ()
2016-01-11 10:55:55.836 BMA.596.2324 ["/ma/dev/devseq.c $Rev: 50728 $ $Date:: 2015-11-09 04:46:51":4010] A.09.00 b105
SeqWrite: (Tape0:0:1:0C): SCTL_Write()=-1: {1026}
My DP release is 9.05