LabVIEW RT Version Mismatch When Connecting to a Real-Time Target

Updated Aug 1, 2023

Reported In


  • CompactRIO Controller
  • PXI Controller
  • Controller for Compact FieldPoint


  • LabVIEW Real-Time Module
  • LabVIEW
  • LabVIEW Real-Time Module
  • Measurement & Automation Explorer (MAX)

Operating System

  • PharLap
  • Linux
  • NI Linux Real-Time

Issue Details

When I attempt to connect to my real-time controller from my LabVIEW project or deploy code, I get the following error: 

Access Denied: LabVIEW RT communication protocol version mismatch.


Access denied: This target is running a version of LabVIEW Real-Time that is different than the Real-Time Module software on the host computer.  You can verify the version and reinstall the Real-Time software using Measurement & Automation Explorer.

Why am I getting this error?


This error occurs when the host machine has a different version of the LabVIEW Real-Time Module installed than the one on the target controller. To resolve this error, install the same version of the LabVIEW Real-Time Module on the controller as the version of the LabVIEW Real-Time Module you are deploying the project from by following these steps:

  1. Expand the Software section under My Systems in Measurement & Automation Explorer and note the LabVIEW Real-Time version that exists on the host. You can also select Help>>About LabVIEW in your development environment to confirm the version of LabVIEW you are deploying your project from.  
  2. Expand the Software tab of the controller under Remote Systems and note the LabVIEW Real-Time version that exists on the target. The error message occurs if these versions are different.
  3. Reformat your controller and install the same version of LabVIEW Real-Time on the target that is on the host. Right-click the Software tab for the RT target and click Add/Remove Software. This allows you to install the version of LabVIEW RT from the host onto the controller. The image below shows the window you will see after selecting Add/Remove Software.

Additional Information

When installing software to your real-time target, the LabVIEW Real-Time Software Wizard should default to use the latest versions of software available on the host PC.

If you choose to re-install/update existing software on your RT controller, the install can fail if you are missing dependencies for the software components you are trying to re-install/update. To get past this, avoid re-installing/updating components separately. Instead use the re-install all option from the real time software wizard software selection screen.

NI MAX only allows you to install existing software onto the cRIO that you have on your computer. Therefore, software should be installed in the following order on the local host computer:
  1. First install LabVIEW
  2. Then install LabVIEW Real-Time (and LabVIEW FPGA Module if you are using it)
  3. Afterwards, install NI-CompactRIO or NI-RIO driver
  4. As last step, install software to your cRIO from NI MAX