Visual Studio Load Testing 'The remote name couldn't be resolved'

I'm trying to make load testing on visual studio 2015. I have this problem and I don't know how to resolve this issue.

at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult) at Microsoft.VisualStudio.TestTools.WebStress.WebTestTransaction.ResponseReceived(IAsyncResult result)

Does anybody knows how to pass this?

thanks.