Volume License Manager (VLM) Fails to Launch with Unknown Error

Updated Jun 26, 2025

Reported In

Software

  • Volume License Manager

Issue Details

Every time I try to open NI Volume License Manager I receive an error message stating:

An unknown error has occurred. Contact National Instruments for technical support at ni.com/support

Solution

Typically, this error indicates corruption in one of the configuration files. This may happen if the server is powered off unexpectedly, especially if it is hosted on a virtual machine.

There may be several ways to fix this issue:

 

  • Restart the NI License Server service.
  1. Click Start» Control Panel» System and Security» Administrative tools» Services.  
  2. Locate NI License Server.
  3. Right-click and select Stop.
  4. Right-click again and select Start

Volume License Manager (VLM) Fails to Launch with Unknown Error.png 
This should reset the VLM data and remove any kind of corruption, so the next time that you launch Volume License Manager the NI VLM Getting Started Wizard will appear. 

Note: This process will remove your current VLM configuration (license file, user/computer information, client permission, etc.) In order to pull your previous VLM configuration, follow the steps to restore VLM with a backup file: Restoring NI VLM from a Backup File

Additional Information

  • If none of the steps mentioned above worked, please consider force reinstalling the NI VLM on your computer.
  • It is important to be aware of potential conflicts with other license server tools installed on the same machine, particularly with FlexNet Publisher. These conflicts can prevent VLM from launching correctly and may result in errors. To minimize these issues, we strongly recommend dedicating a separate server to host NI Volume License Manager, however, if this is not possible, please refer to this article Can I Run Both NI Volume License Manager and Another License Server On the Same Machine? for guidance on how to configure two servers to coexist.