"Cannot Create Unknown Type" Packages Present In NuGet Folder But Marked As Unsafe

Not able to invoke process, Error fix for : RemoteException wrapping System.Xaml.XamlObjectWriterException: Cannot create unknown type( http://schemas.microsoft.com/netfx/2009/xaml/activities}Variable({http://schemas.uipath.com/workflow/activities}DatabaseConnection).

Getting the error "Cannot create unknown type" for specific packages. This issue happens when a job is not able to find the package mentioned in the error due to the following reasons:

  • The package is available in the nuget folder but was copied from a different environment and hence it was marked as unsafe.
  • The Robot is not able to reach he Nuget or MyGet feeds to download the package.


  1. If the Robot machine is restricted from accessing the internet and the customer is manually copying the packages then make sure packages are marked as safe. Open the property of the .dll causing the issue (.nuget\packages\uipath.database.activities\1.2.6863.32528\lib\net40-client\) and select the unblock checkbox. Reference: Blog - System Not Supported Exception
  2. If there is no internet restriction, check the proxy configuration and also make sure the services mentioned in the below article are accessible: