+1 805-541-1003

External Tool Failure (Revit Add-in) Revit Cannot Run the External Application "Land F/X", System.IO.FileLoadException (Using One of Our Revit Plugins)



You received one of the following error messages after installing the Land F/X Revit 3D Connection plugin and opening Revit:

External tool failure

Revit cannot run the external application "Land F/X". Contact the provider for assistance. Information they provided to Revit about their identity: Land F/X,


Could not load file or assembly




Could not load file or assembly LandFXRevitAddin.dll, or one of dependencies. Operation is not supported. Exception from HRESULT 0x80131515.



A security setting on your computer has added a block to the add-on’s DLL (.dll) file.



You can resolve the issue by unblocking the DLL file on your computer manually:


1. Navigate to the file LandFXRevitAddin.dll file. It will be at the following path: C:\Users\(USERNAME)\AppData\Roaming\Autodesk\Revit\Addins\(YOUR VERSION)\LandFXRevitAddin.dll (where USERNAME is your computer username).




2. Right-click the DLL file, and select Properties from the menu that opens.




3. If you have this issue, you’ll see an Unblock button.


Click this button, then click Apply and click OK.




4. Restart Revit. You should no longer see the error message, and the Land F/X add-in will be installed.

Last modified on Sep 12, 2019


  • Land F/X

Our software tailors AutoCAD to the needs of landscape architects, irrigation designers, and other professionals. We automate your most tedious tasks and ensure accuracy, giving you more time to design.

Log in to