Your sitefinity version is not supported - 5.1.3270
When will Thunder be able to work with version 5.1.3270?
Sitefinity Thunder has had support for 5.1.3270 since its the 220.127.116.11 version has been released (3 August). Please check your Sitefinity Thunder version. You can update your Sitefinity Thunder Visual Studio extension from Visual Studio by going to Tools -> Extensions Manager -> Updates, or by going to Visual Studio Gallery to download the installation file manually.
the Telerik team