Question Marks in Block Diagram

Updated Feb 27, 2023

Reported In


  • LabVIEW


  • Tektronix
  • Agilent
  • Keysight
  • Keithley
  • Ocean Optics
  • Eurotherm
  • Additional companies

Issue Details

  • I downloaded a third-party instrument driver from the NI website. When I open an example VI from the downloaded folder, the block diagram shows many blocks with question marks. How do I get rid of the question marks?
  • My VI project is no longer working. One of my VIs now has question marks on the various subVIs in the block diagram. How do I fix it?


If the icon has a question mark, or the functions palette is blank, the file or driver folder that the icon points to has either been:
  • Moved to the wrong place or location on your computer
  • Deleted from the expected location on your computer
  • No longer exists on your computer
The missing file may be a .mnu or .vi file depending on whether the icon represents a sub-palette or VI. If a whole palette is full of question marks, this indicates that the file containing these VI's does not have the correct file path relative to the .mnu file to which it’s governing palette icon points.

In order to get rid of the question mark blocks,
  1. The expected file path for the driver folder or file must be determined
  2. The appropriate driver folder or file must be placed in this location. Make sure there are no intermediary files in the path that do not belong.

Determine the Expected File Path for the Driver Folder or File

In order to find the correct file path of the folder utilize one of the following resources in the LabVIEW VI:
  • Context Help
  1. Turn on Context Help by pressing Ctrl-H on your keyboard.
  2. Hover over the Question Mark block to see its expected file location in the Context Help Window.
  • Palette Settings
  1. Go to Tools » Advanced » Edit Palette Sets...
  2. Three windows will pop up: the Edit Controls and Functions Palettes window, (b) the Controls window, and (c) the Functions window.
  3. In the Functions window, navigate to the icon with the question mark.
  4. Right click and select Display Path to Menu File...
  5. The window that pops up will provide the expected file path for that particular icon

Check the Expected File Path for the Desired Driver Folder or File

  • Common Locations
    • Instrument Drivers: <Program Files>\National Instruments\LabVIEW XXXX\instr.lib
    • 3rd Party Add-On's: <Program Files>\National Instruments\LabVIEW XXXX\vi.lib
  • Initial Troubleshooting Steps
    • If the expected driver folder or file is not in the expected location, but there are some files and folder present at the expected location, check the following:
      • The driver's folder that was unzipped could have been renamed by the user.
      • The driver's folder was put into an extra folder inside the instr.lib or vi.lib folder.

Re-download the Expected Driver folder or VI, if needed

If the expected third-party driver or instrument driver is not at the expected file path, acquire the necessary library and place it in the proper location. NI provides the following ways to access third-party driver downloads: Additional drivers can sometimes be found by searching the device make and model, but these drivers are not guaranteed or supported by NI.

Additional Information

When you first open the example VI, LabVIEW will look into a specific file path for the subVIs in the program. If the Instrument Driver folder is not saved in the correct file path, LabVIEW will lose reference to where the files are located. The VI will thus be represented by question mark block in LabVIEW.

Note: Once the folder has been moved to the correct file path there should not be any .mnu files in the instrument driver folder. If there are, these files must be removed in order for LabVIEW to recognize the VIs. 

Disclaimer: Third-party add-ons for LabVIEW , available on our website, are offered by independent third-party providers who are solely responsible for these products. NI has no responsibility whatsoever for the performance, product descriptions, specifications, referenced content, or any and all claims or representations of these third-party providers. NI makes no warranty whatsoever, neither expressed nor implied, with respect to the goods, the referenced contents, or any and all claims or representations of the third-party providers.