Unable to Communicate With License Server Error in NI VLM

Updated Jun 12, 2024

Reported In


  • NI License Manager
  • Volume License Manager

Issue Details

  • I want to use an NI Software product that is licensed through NI Volume License Manager (VLM). Whenever I launch the product, when attempting to connect to the license server I get the following message:
     Unable to Communicate With License Server. 
  • My local licenses in NI License Manager are in evaluation mode or appear as unlicensed. 
  • When I open NI License Manager and try to connect to a license server I receive the error below. 
Could not contact server

  • I was able to connect to the license server but there was no Manage button. Even though the server has assigned a license to me, the icon did not turn green.

No Manage Button.png


This issue can have multiple causes. Below are suggested solutions:

The client may not have network access

If the client does not have network access and cannot connect to a license server at all, you can generate a disconnected license file from NI VLM following the steps found in Getting Started with NI VLM: Creating a Disconnected or Home License.


Make sure you are connecting to the Volume License Server

Ensure you are connected to the Volume License Server for your organization. This can be checked in NI License Manager under "Network Licenses" and looking under the server name. If no server name appears, you can add a server by going to the blue book tab and selecting "Manage Volume License Servers," where you can add the name of one.

You can verify the name you are entering matches the Volume License Server name by talking to your software admin.  

NI Volume License Manager might be out of date

New versions of NI software might require the latest version of VLM because of the version of NI License Manager that it installs on the client machine.
To check the compatibility between the NI License Manager and Volume License Manager versions that you have installed visit the NI License Manager Release Notes page, choose the version of NI License Manager you have installed, and see the Readme file.
Instructions on how to update VLM and create a backup can be found in this article.

The License File might be out of date

In case you are trying to activate a newer version of NI Software that is not included in your license file you will receive an error "Unable to connect to the Server". 
Please determine that you are using an updated license file, in case you aren't please obtain a new license file from NI.

NOTE: NI provides its customers with new license files in an email at the time of releasing a new software version that customers barely miss (lands in the SPAM folder) or ignore. 
If customers do not install this updated license file on their server, they will be able to activate only the versions that were available at the time their last license file was created.
For example: In the case of LabVIEW, NI releases new versions every spring and autumn and this time provides its customers (where LabVIEW is included in a Volume License Agreement) with updated license files including the latest versions of LabVIEW.


The license server may be down

  • Ensure that the server computer is on and that the license server is running.
  • Verify that the license server is running without an error. This can be done by examining the log file or by stopping and restarting the server. 
  • If an error has occurred, you may get a message saying Unable to stop license server. In this case, stop the nilm.exe process through the Windows Task Manager. Then restart the license server.
  • Reboot the server.

The client computer may not be pointing to the correct license server port

  1. Check the port that the license server is running on (NI-VLM >> Tools >> Preferences >> System Settings).
  2. Ensure that the client computer is configured to look to that same port:
    1. Open NI License Manager by going to Start»All Programs»National Instruments»NI License Manager.
    2. Go to Top Left Tab>>Manage Volume License Server. 

    3. Ensure that the correct server name and port are configured (ports are specified using Server:##### syntax).
  3. If you cannot connect to the server you can do a Telnet connection test to test the connection between your client machine and the server by following Testing VLM TCP Communication Ports Using Telnet.


The firewalls on the VLM server-side may be blocking some or all of the ports necessary for client-server communication

The following instructions are for Windows 7, refer to Microsoft documentation for similar instructions in other operating systems: 
  1. On the Start Menu in Windows, click Control Panel.
  2. In Control Panel, click System and Security, and then open Windows Firewall.
  3. In Windows Firewall, click Advanced Settings, and then click Inbound Rules.
  4. On the right-hand side bar, select New Rule... to open the New Inbound Rules Wizard.
  5. Within the Wizard, configure the port rules such that TCP 27000 and 4637 are open, per Configuring Software and Hardware Firewalls to Support NI Products. Note: these TCP ports correspond to the Main Licensing and Communication ports as configured in the NI Volume License Manager. Confirm the VLM ports that need to be opened in Tools >> Preferences >> System Settings.

Note: Firewall connections may be controlled by your IT Department or Computer Administrator. If the activation is not successful after configuring the ports, check with IT to see if they are blocked elsewhere.


The client may not be on the same domain as the license server

This error might occur if the client computer is connected to a license server that is on a different domain than the client computer. To resolve this, add the server's domain to the client computer's DNS settings. To do this, complete these steps on the client's computer to verify the domain .