ShadowSnap Agent: Backup failed as Backup job was unable to be assigned



Backups fail with the error: Backup failed as Backup job was unable to be assigned (500, 401, 403, 404) / Job Assign Failed! and the error code: Job assign failed! -403/401/500


  • Datto ALTO
  • Datto SIRIS
  • ShadowSnap Agent


If you are encountering an intermittent 401 error after an uninstall and reinstall of the ShadowSnap agent, see this article for potential causes and resolution.
  • The ShadowProtect, StorageCraft ShadowCopy Provider, or StorageCraft Raw Agent service may not be running on the protected system. See section 3.1. Check for services.
  • The key file created during the registration pairing between the ShadowSnap Agent Service & the Datto Appliance may have been interrupted. See section 3.4. Repair agent communications.
  • A proxy server or network security element may be interrupting communication between the ShadowSnap Agent and the Datto Appliance.
    • The local firewall settings are blocking/filtering ports 25566 and 139.
    • The server's local DNS is unable to resolve
     See section 3.2. Network settings.
  • The ShadowProtect license is expired due to un-installation and re-installation of ShadowProtect. See section 3.3. Check the license.
  • All volumes have been excluded for backup from the advanced options tab. See section 3.5. All volumes excluded from backup.
  • The backup engine has not been populated. See section 3.4. Repair agent communications.
  • A backup job may think it's currently in transit. See section 3.4. Repair agent communications.

Figure 1: Backups fail with 401 error 

In addition, the link "Show Agent Log" displays the following error:Figure 2: The agent log

Additional possible cause

If agents take constant full backups or differential merges at random intervals, or encounter intermittent 401, 500, or VSS writer errors, there may be more than one Datto appliance on the network trying to back up the same protected machine.

Datto does not recommend protecting a production system with more than one Datto appliance at the same time. Even if they have different scheduled backup times, both systems cannot work in tandem with each other, because they both store information in the same location on the protected server with the same naming schemes, and will overwrite each others' changes to those files. 


Follow these steps to resolve this problem:

Check for services

Check that all 3 services are present on the target machine via services.msc

  • StorageCraft Raw Agent
  • StorageCraft Shadow Copy Provider
  • ShadowProtect Service

Stop the StorageCraft ImageReady service. Then, right click the service and go to Properties. Change the Startup Type to Manual

Open up task manager, and end the processes of any instances of the following services:

  • raw_agent_svc.exe
  • ShadowProtect.exe
  • ShadowProtectSvc.exe
  • vsnapvss.exe

Restart the services through the services.msc console.

 Network settings

Ensure that all Local/Edge hardware or software have the proper exceptions configured. Depending on the software/hardware, you will need the following information:

  • Website:
  • IP address:
  • Local Service: ShadowProtectSvc.exe

To view the proxy settings use the following commands from a CMD prompt:

  • Proxycfg.exe: Proxycfg.exe
  • Netsh.exe: Netsh winhttp show proxy (with Vista / Server 2008 or newer)

Reset the proxy to "Direct," which will delete any entries listed.

  • Proxycfg.exe: Proxycfg.exe –d
  • Netsh.exe: Netsh winhttp reset proxy (with Vista / Server 2008 or newer)

Check Windows Firewall or any Antivirus to make sure exceptions exist for the ShadowSnap application to access ports TCP 25566 and TCP 139.

Check the License Status

Open up ShadowProtect and determine the license status:


The license should read as active.

  • If the license shows expired, follow the steps in the Repair Agent Communications section of this article to re-pair the agent with your Datto appliance. The ShadowProtect software will automatically attempt to reprovision its license during this process.

  • If it is disconnected, retry the steps for restarting the services for ShadowProtect and ShadowSnap. Ensure that the ShadowProtect software is 5.0.x.

Repair Agent Communications

  1. On the Datto device, select Protect and Configure Agent Settings.

  2. At the bottom of the Configure Agent Settings page, click the Repair Agent Communications button.


  3. Check the volumes on the advanced options tab, and ensure that the correct volumes are selected for backup.

  4. Under basic options, change the backup engine to a different engine.

  5. The agent may think a backup job is already running. To fix this, rename the database where the job state is residing.

  6. Open services.msc, and stop the StorageCraft Raw Agent.

  7. Navigate to C:\Program Files (x86)\StorageCraft\ShadowProtect\ShadowSnap.

  8. Find the file called endptconfig.sqlite3 in that folder. Rename that file to .old

  9. Restart the StorageCraft Raw Agent Service.

  10. Repair agent communications on the device, and attempt another backup job.

3.5. All volumes excluded from backup

A protected system's backup jobs would fail if all volumes are excluded from backup. To check if this is the case for your system, follow these steps:

  1. In the device web interface, click Protect and go to Configure Agent Settings for the protected system.
  2. Go to the Advanced section and check the settings in Volume Level Backup Control. Make sure that at least one volume is not excluded.

If you have attempted all troubleshooting steps described in this article and are still experiencing backup failures, please contact Datto Technical Support for further assistance.

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