Error "Querying plugins failed" in the client Backup tab dialog using 21.2.404 and 21.2.422 on a Windows Server 2025 24H2 (April 2025 Updated) OS, that is acting as a Domain Controller (any DC type), if UAC (EnableLUA = 1) is enabled in the OS (it is default enabled in that OS, and it will normally be enabled in that OS out of the box we think); no plugins will list & any (existing) backup jobs that do contain any plugins in the selection will fail totally, to the 'Local' and 'Cloud Backup' modern backup devices at least, including if the existing backup job was a combination files + plugins backup job in that case, using the 21.2.404 and 21.2.422 client versions at least (but it will likely also be true for older client versions we think).
- Plugins query will fail altogether in the backup client on Windows Server 2025 (All OS editions, including the DataCenter and Standard editions) 24H2 (April 2025 Updated) OS that is promoted as a Domain Controller (for all DC types), if UAC is enabled in OS; no plugins will list and backup jobs that did have any plugins in them will fail totally (because the NBK plugins query will fail). In order to see this NBK client plugins query issue the only role on that OS that must exist is the "Active Directory Domain Services" role, and the machine has to be promoted as a Domain Controller (DC). However, if the machine is not acting as a Domain Controller then this problem won't be true and seen. Even if you do not need to backup a specific plugin the issue will make it so that no plugins can backup. For now we know that this client NBK plugins query issue can be worked around by disabling UAC in the registry with the command described here; and then do a reboot after that. For more details read the how-to KB article here. We will look at how to not require that workaround in a future release.
We have seen that after doing an internal test on a Windows Server 2025 24H2 (April 2025 Updated) OS machine, that is acting as a Domain Controller, if UAC (EnableLUA = 1) is enabled in the OS (it is default enabled in that OS, and it will normally be enabled in that OS out of the box we think), as detailed in the 2nd entry in the "Known issues and limitations with this version" section for the 21.2.422 client version, in the Changelog KB article here, that the Plugins query that runs in the client when clicking on the "Backup" tab in the client GUI app will fail with "Querying plugins failed" error, with an error at the bottom left of the "Backup" tab dialog, which is where the plugins would normally be listed at, that states: Querying plugins failed. In our initial internal testing on one such machine, that meets the OS specs in the first sentence, that issue can be worked around by disabling UAC EnableLUA = 0 in the registry with the command described here, or you can use our own more complete stated instructions steps below; and then do a reboot after that.
Simple workaround Instructions steps:
Start a "Windows PowerShell" (right-click and Run as administrator) app or a “Terminal (Admin)” app prompt in Windows Server 2025 24H2, that is acting as a Domain Controller, don't start an Admin Command Prompt though as the set of commands to run won't work there, while logged in as an administrator user, first to read what the current “EnableLUA” property value is, to read back that current property value to you with a get command, so that you know what it is, and then you will issue a set command to disable UAC (EnableLUA = 0) after that first get command:
Get-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System" -Name "EnableLUA"
In the above get command output should in the first line of the output state if the current "EnableLUA" variable value is a 0 or 1, meaning is disabled or enabled. It likely in your case is enabled and has a 1 for that value, which means that UAC is enabled in the OS, as that is the out of the box default setting in the Windows Server 2025 24H4 OS. The next set command stated below will disable UAC (EnableLUA = 0); which will 100% require a reboot after this change and step:
Set-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System" -Name "EnableLUA" -Value 0
After the above set command is issued, if the command was entered in properly, a pop-up dialog in the system tray area of Windows may (but I did notice that sometimes it does not do this though, even though the above settings change was done correctly at this point) display for a few seconds, right at that point that you pressed the <enter> key on that above command, that will state "You must restart your computer to turn off User Account Control", and it is 100% the case that for UAC to be disabled you must reboot the machine, so do that reboot now. And then only after the reboot, you can test the NBK plugins query process again and the "Backup" tab dialog should work without the plugins query failing problem, and without the subsequent plugins backup failing problem after that is done:
And then after you have verified that the NBK plugins query can complete without the "Querying plugins failed" error message problem in the "Backup" tab dialog (which should also be true for future reboots), with UAC (EnableLUA = 0) disabled in the OS at that point, which at this point is a completely optional step to need to do (but it may be that your security policies would advise not leaving UAC completely disabled in the OS in that case, as to the reason why you may want to re-enable it at this point, but just know that if you do re-enable UAC that the same NBK plugins query will fail, and backup jobs that have any plugins in the backup job selection will also fail, problem will return after that), if you would like to re-enable UAC (EnableLUA = 1) to revert that setting back to what likely was the default OS setting value (if that first get command had showed that it was enabled in the OS), you can issue this set command:
Set-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System" -Name "EnableLUA" -Value 1
And right after issuing the above command and pressing <enter> on it, if the command was entered in properly, a pop-up dialog in the system tray area of Windows will display for a few seconds, right at that point that you pressed the <enter> key on that above command, that will state "You must restart your computer to turn on User Account Control", and it is 100% the case that for UAC to be re-enabled you must reboot the machine, so you will need to do that next, but only if you did do this completely optional step (to revert the UAC setting back to the, most likely, defaults):
Note: This issue will likely also affect earlier versions of the backup client, not just the 21.2.404 and 21.2.422 clients that are stated in this KB article. It is also possible that the same issue will affect other OS's, but the only known OS to report about right now is listed in the KB article, and if that becomes untrue we will update the article to state any other OS's or versions of OS's that have been known to also be affected by this issue at that later time. It is possible that we may resolve this issue in the code, but for now you can utilize the provided workaround as long as it meets your environment requirements.
Note: The separate "Create Image" function dialog will fail to create an Advanced method boot media problem, that is discussed in the how-to KB article here, does seem to affect the same Win Server 2025 24H2 OS that shows this "Querying plugins failed" problem, at least in the backup client, in that case.
Edit: If you aren't willing to perform the stated workaround to disable UAC ("EnableLUA = 0") in the OS completely, to workaround this or other stated issues in NovaBACKUP, for instance due to security or corporate policy concerns, as to it is not feasible to implement that change, then as an alternate method of workaround to at least try out and then utilize if it can work in your case (but you must know about the two items that are downsides to using this alt. method of workaround), you can also change the "nsService" service (which is the "NovaBACKUP Backup/Copy Engine" service name) "Log On As" setting to a Domain Administrators group user, that could be your primary user or it could be a "NovaBACKUP" user even, as long as that Domain user is a member of the "Domain Administrators" group, and then restart that same service. Just know that if you do implement that alt. workaround method that two things will be true, that A. the "Run As" setting for all job types will become unusable for if it is set to utilize "Run as specified user" then running those backup jobs will immediately fail with a service exception, because the nsService itself you told to be permanently assigned to a single user already, the client software will be locked to that one user for all functions, and B. that settings change won't survive future NovaBACKUP client upgrades, as the setting will become reversed back to the default "SYSTEM," user, so you'd need to remember to reapply that change after every client upgrade or client repair action. Also, there is a chance that if you do this alternate workaround method, that Image Backup (DR) functions may break and show issues after that change, and in general we don't recommend that the nsService be changed from the defaults (as it tends to cause problems in various functions, so you need to be aware of that fact before choosing to go with the alt. method of workaround in that case).