Verify that pbx_exchange and nbemm are running.

Examine command output, debug logs, and system logs for a more detailed message on the error.

Run the tpconfig -d or vmquery -a command to verify that the EMM server is actively running and that it accepts new connections.

For a DA reserve drive request, verify that another host had not already reserved the drive.

For a DA release drive request, verify the following: that the drive is DA reserved by the host requesting the DA release and has not already been released.