The key is in this statement:
"My devbra -dev shows nothing ".
Whenever you access a media device for any reason, the 'devbra -dev' is always done first.
Make sure that your OS is seeing the devices by going into the Device Manager on the System that is controlling to robotics and/or drives. Are you seeing "Media Changer"? Are you seeing Drives? If you expand either one, is it saying 'Unknown'?
If not, you should probably reboot the tape library, then, reboot the Media Agent that controls the Robotocs and/or the drives, and check the Device Manager again. If nothing has changed, check for a problem with the physical connection to the tape library, like an in-plugged cable, or a problem with the SCSI terminator
If the Device Manager looks OK, make sure that you are up to date with drivers for the Media Changer and Drives. You may also want to try disabling the drivers (DP will take it either way) by right-clicking on the device, and picking Disable, and run the 'devbra -dev again
