The dialog and the watermark stating that no license is found are displayed, even when the license key is installed properly. This happens in addin projects, like Excel VSTO Add-in.

To workaround this use the  TelerikLicensing.Register method to install your license script key.

public MyWpfUserControl()
{
    TelerikLicensing.Register("your-script-key");
    InitializeComponent();
}