Registering plugin problem

Dear all,

I am trying to automatically register a Rhino plug-in under Windows 10 via a registry entry like described here.

On first startup of Rhino6 after installing the plug-in, I get the following error: 'Unable to load …rhp plug-in: no class derived from CRhinoPlugIn in plug-in file. After hitting ‘OK’ Rhino starts normally and the plug-in works correctly. Checking Tools/Options/Plug-ins shows that the plug-in was loaded three times.
When I close and open Rhino again no error message shows up and everything works.

The problem seems to be connected with the automatic loading procedure: When I load the plug-in via drag and drop it works with no error message showing up.

The plug-in was compiled using MSVC 2019 Version 16.4.1, the Rhino version is RH6 SR22 (6.22.20028.13281), the SDK version is 6.22.20028.13281.

Has anyone an idea what might cause the error message?


Update: The problem seems to be connected with the Version of Windows 10. On two of my machines the problem does not occur: with Windows 10 Pro, Version 1709, Build 16299.125 and Windows 10 Pro, Version 1909, Builde 18363.657 everything works fine.

Hi @cp1,

Even though you are using Visual Studio 2019, your plug-in project should still be built with the Visual Studio 2017 (v141) toolset and the Windows SDK Version 8.1.


– Dale

Dear Dale,
thanks for your reply!
I tried out your suggestion and compiled the plug-in with Windows SDK 8.1, and v141 Platform Toolset. It did not solve the problem however.
The problem seems not to be connected with the Windows 10 version. The machine which shows the problem has Windows 10, Version 1909, Build 18363.657 installed.

Hi @cp1,

Can you drag and drop the .RHP file to register?

– Dale

Hi @dale,
drag and drop works without problems.

  • Clemens