Most GP AddIn samples place setup code inside the Initialize() method of the IDexterityAddIn interface. The issue is that Telerik’s licensing system needs the key registered before any Telerik assemblies load. By the time Initialize() runs, it may already be too late, causing licensing exceptions or unlicensed UI behavior.
The Correct Fix
The solution is to register the license key inside the constructor of your AddIn class — specifically the New() method — ensuring the key is applied at the earliest possible point in the load sequence.
1. Go to your account at Telerik and download the Licensing 'EvedinceAttribute'. Exact Steps:
Place this key in GpAddin.vb, in the 'New()'. Not the 'Initialize()':
Public Sub New()
TelerikLicensing.Register("eyJhbGciOiJSUzI1NiIsInR5cCI6IlRlbG...")
End Sub
' IDexterityAddIn interface
Sub Initialize() Implements IDexterityAddIn.Initialize
Try
This got it working for me.
More reading:
https://www.telerik.com/products/winforms/documentation/licensing/license-key#installing-a-license-key-in-projects-by-using-telerik-assembly-references-without-nuget-packages