Question Marks in Block Diagram After Installing 3rd Party Driver

Updated Nov 6, 2018

Reported In


  • LabVIEW


  Some popular 3rd party drivers:
  • Tektronix
  • Agilent
  • Keysight
  • Keithley
  • Ocean Optics
  • Saphira
  • More

Issue Details

  • I downloaded a 3rd party instrument driver from the National Instruments 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 VI's now has question marks on the various sub-VI's in the block diagram. How do I fix it?


To get rid of the question mark blocks, the instrument driver folder, must be saved in the expected file path on your computer.

In order to find the correct file path of the folder perform these steps in the LabVIEW VI:
  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.
  3. The folder must then be moved to this file path. A common location for instrument drivers in LabVIEW is: <Program Files>\National Instruments\LabVIEW XXXX\instr.lib
  4. If the above did not solve your problem, it's possible that LabVIEW cannot find the library. Below are some other errors to watch out for
    • The instrument driver folder that is unzipped is renamed by the user.
    • The instrument driver folder is put into an extra folder inside the instr.lib folder.
If the expected 3rd Party Driver is not in the vi.lib or instr.lib folders, you will need to acquire the necessary library and place it in the proper location. NI provides some access to downloading 3rd party drivers below:

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. 



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