What permissions or settings are needed in VSTS for running cloud based load test?

I am trying to run load test in Visual Studio Team System.

I have properly set all the runsettings and connected our Team Server in the Team Explorer. But when I try to run the load test, it failed with message:

"The action you are trying to perform requires a connection to Visual Studio Team Services. Connect to a Visual Studio Team Services account using Team Explorer and try again."

I am sure that I have connected to the Team Service and am able to do other operations such as pull or push. So I wonder if it is because of some settings about permissions in our Team Server? What permissions are needed for running cloud based load test?

Thanks!