Upon installing Grasshopper some files of the Karamba3D package may have been erased. Try to reinstall Karamba3D.
Make sure to unblock the Karamba3D installation (*.msi) file before running the installation. To do this, right click on the file in Explorer and go to "Properties". If the file is blocked, there will be an option to "Unblock" the file at the bottom of the Properties Window.
Ensure that you install Karamba3D as an administrator.
Check the directory where Karamba3D is installed. It should be located in the Plugins folder of the Rhino installation. This is often C:\Program Files\Rhino 6\Plug-ins or C:\Program Files\Rhinoceros 5.0 (64-bit)\Plug-ins, however it can also be C:Program Files\Rhinoceros 5 (64-bit)\Plug-ins. Make sure the folders correlate otherwise Karamba3D will not appear in Grasshopper.
In case of multiple versions of Rhino on your machine make sure that you installed Karamba3D to that right version. Karamba3D can be installed for “Rhinoceros 5 (64-bit)”, “Rhino 6” and “Rhino 7” in parallel. In that case there will be three “Karamba3D” entries in the list of installed applications.
You can also navigate to the Plugins folder of your Rhino installation (C:\Program Files\Rhino 6\Plug-ins for example) and drag and drop the Karamba.gha file into your Grasshopper canvas.
When installing Karamba3D on Windows 8, and an error message pops up stating ‘There is a problem with this Windows Installer Package. A DLL required for this install to complete could not run. Contact your support personnel or package vendor.’ do the following:
Make sure that you installed a Karamba3D version with the correct bitness: Karamba3D (64bit) can be used together with Rhinoceros 5 (64bit); Karamba3D (32bit) with Rhinoceros 5. Be aware of the fact that both versions of Rhino get installed.
Check to see if the installation file downloaded contains the *.msi extension. Sometimes Windows automatically adds an *.exe extensions to *.msi files.
Make sure that Windows is up to date.
Change the permissions to full access to ‘C:\Users\<username>\AppData\Local\Microsoft\Windows or C:\Users\<username>\AppData\Local\Temp’. Make sure that the hidden files and folders are shown in Windows. Open Windows Explorer and folder ‘C:\Users\<username>\AppData\Local\Microsoft\Windows or C:\Users\<username>\AppData\Local\Temp’. Right click on the folder, the Local Properties pop up window will appear. Select the tab Security. Click Edit, the Permissions for Local pop up window will open. On Group or _user names, select the desired user. Ensure that the Allow check box for Full control is activated, else activate it. On the Permissions _for Local pop up window, click OK (if no changes were made) or Apply (if changes were made). On the Local Properties pop up window, click OK (if no changes were made) or Apply (if changes were made).
See Pix4d for further support