One of the known reason is mentioned in this article: https:// .Other reason could be; presence of faulty media which cannot be consumed by Backup Exec to perform the backups.Perform an Inventory to make sure all OST Media(s) are readable.Restart all Backup Exec and Deduplication services.Great care should be taken when making changes to a Windows registry.Registry modifications should only be carried-out by persons experienced in the use of the registry editor application.Queue processing can be manually triggered by running --processqueue from command prompt (run from BE Install path.
It may caused by the kind of resource we are backing up or something else outside of deduplication storage but affecting the backup and it could also be something within Dedupe.
From BE Install Path\ --test this tests the file in Dedupe\etc\Puredisk.
If this file is tampered then Deduplication Engine will not start (call support to rectify the file) Backup Exec Deduplication Engine may not start if any bin or bhd file goes missing from Dedupe\Data folder.
Note: While creating or re-importing a Deduplication Storage Folder in Backup Exec, needs to be referred if an error is seen while creation/re-import. See Deduplication Folder creation or recreation fails with "An Error Occurred while Creating the deduplication storage folder".
Sometimes it may be required to delete the Etc Path and Config File Path String Value from the following Windows Registry location: HKEY_LOCAL_MACHINE\SOFTWARE\veritas\Pure Disk\Agent. Incorrect use of the Windows registry editor may prevent the operating system from functioning properly.