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

See "Setting Media Manager debug logging to a higher level" in the NetBackup Logging Reference Guide.

Investigate the system log messages that are related to the specific error leading to the media mount failure. Verify that all of the Media Manager binaries are at a compatible version level.

Verify that the robotic interfaces to vendor and operating system software have compatible versions.