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Error "Querying plugins failed" in the client Backup tab dialog on Win Server 2025 24H2 (April 2025 Updated) OS, that is a Domain Controller, if UAC is enabled in OS; no plugins will list & backup job

"Querying Plugins Failed" Error on Windows Server 2025

Problem

You see an error message "Querying plugins failed" at the bottom of the Backup tab in the NovaBACKUP client on Windows Server 2025 (24H2 April 2025 update).

What this means: Your backup plugins won't load, and any existing backup jobs that include plugins will fail completely.

Affected Setup:

  • Windows Server 2025 (24H2 - April 2025 update) configured as a Domain Controller
  • NovaBACKUP client version 21.2.404 or later
  • User Account Control (UAC) is enabled in Windows (this is the default)

Root Cause

When Windows Server is configured as a Domain Controller with UAC enabled, the NovaBACKUP client cannot query its backup plugins. This prevents the software from loading or running plugin-based backups.

Solution: Disable UAC (Recommended)

⚠️ Important: You must reboot your server after making this change.

Step 1: Open PowerShell as Administrator

  1. Right-click on Windows PowerShell
  2. Select Run as administrator

Do NOT use Command Prompt—the commands won't work there.

Step 2: Check Current UAC Status

Run this command to see if UAC is currently enabled:

Get-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System" -Name "EnableLUA"

Expected result: You'll see EnableLUA with a value of 1 (enabled).

Step 3: Disable UAC

Run this command:

Set-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System" -Name "EnableLUA" -Value 0

A popup may appear saying "You must restart your computer to turn off User Account Control."

Step 4: Reboot Your Server

Restart the server for the change to take effect.

Step 5: Verify the Fix

After reboot, open the NovaBACKUP client and click the Backup tab. The plugins should now load without errors.

Alternative Solution (If You Cannot Disable UAC)

If your security or corporate policies prevent disabling UAC, you can try this workaround:

  1. Open Services (services.msc)
  2. Find "NovaBACKUP Backup/Copy Engine" (nsService)
  3. Right-click and select Properties
  4. Click the Log On tab
  5. Change the login account to a Domain Administrator user
  6. Restart the service

⚠️ Important Limitations:

  • The "Run As" feature for jobs will stop working
  • This setting resets to default after software updates or repairs
  • Image Backup (DR) functions may experience issues
  • We do NOT recommend this approach for long-term use

Re-enabling UAC (Optional)

If you need to re-enable UAC for security reasons, you can reverse the change:

Set-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System" -Name "EnableLUA" -Value 1

Note: Re-enabling UAC will bring back the "Querying plugins failed" error. The error will persist until NovaBACKUP releases a permanent fix.

Related Issues

You may also experience the "Create Image" function failing on the same Windows Server 2025 setup with UAC enabled. This is a separate known issue with a separate KB article available.

Questions?

Contact NovaBACKUP Support if you need additional help.