how to run a Load Test automatically on tfs

i was trying the whole day to get it run but i was unsuccessful. maybe someone here already did it and could tell me what i must do to get it run.

locally it works perfect but on the tfs i get errors like:

2017-07-26T11:53:31.9384935Z ##[error]System.Management.Automation.MethodInvocationException: Exception calling "FindServicePoint" with "1" argument(s): "This operation is not supported for a relative URI." ---> System.InvalidOperationException: This operation is not supported for a relative URI. 
2017-07-26T11:53:31.9384935Z ##[error]   at System.Uri.get_IsDefaultPort() 
2017-07-26T11:53:31.9384935Z ##[error]   at System.Net.ServicePointManager.MakeQueryString(Uri address) 
2017-07-26T11:53:31.9384935Z ##[error]   at System.Net.ServicePointManager.FindServicePointHelper(Uri address, Boolean isProxyServicePoint) 
2017-07-26T11:53:31.9384935Z ##[error]   at System.Net.ServicePointManager.FindServicePoint(Uri address, IWebProxy proxy, ProxyChain& chain, HttpAbortDelegate& abortDelegate, Int32& abortState)
2017-07-26T11:53:31.9384935Z ##[error]   at CallSite.Target(Closure , CallSite , Type , Object ) 
2017-07-26T11:53:31.9540903Z ##[error]   --- End of inner exception stack trace ---
2017-07-26T11:53:31.9540903Z ##[error]   at System.Management.Automation.ExceptionHandlingOps.ConvertToMethodInvocationException(Exception exception, Type typeToThrow, String methodName, Int32 numArgs, MemberInfo memberInfo)
2017-07-26T11:53:31.9540903Z ##[error]   at CallSite.Target(Closure , CallSite , Type , Object )
2017-07-26T11:53:31.9540903Z ##[error]   at System.Management.Automation.Interpreter.DynamicInstruction`3.Run(InterpretedFrame frame)
2017-07-26T11:53:31.9540903Z ##[error]   at System.Management.Automation.Interpreter.EnterTryCatchFinallyInstruction.Run(InterpretedFrame frame)
2017-07-26T11:53:32.2978722Z ##[error]System.UriFormatException: Invalid URI: The hostname could not be parsed.
2017-07-26T11:53:32.2978722Z ##[error]   at System.Uri.CreateThis(String uri, Boolean dontEscape, UriKind uriKind)
2017-07-26T11:53:32.2978722Z ##[error]   at Microsoft.PowerShell.Commands.WebRequestPSCmdlet.CheckProtocol(Uri uri)
2017-07-26T11:53:32.2978722Z ##[error]   at Microsoft.PowerShell.Commands.WebRequestPSCmdlet.GetRequest(Uri uri)
2017-07-26T11:53:32.2978722Z ##[error]   at Microsoft.PowerShell.Commands.WebRequestPSCmdlet.ProcessRecord()
2017-07-26T11:53:32.2978722Z ##[error]   at System.Management.Automation.CommandProcessor.ProcessRecord()
2017-07-26T11:53:32.4385116Z ##[error]System.Management.Automation.RuntimeException: You cannot call a method on a null-valued expression.
2017-07-26T11:53:32.4385116Z ##[error]   at CallSite.Target(Closure , CallSite , Object , String )
2017-07-26T11:53:32.4385116Z ##[error]   at System.Dynamic.UpdateDelegates.UpdateAndExecute2[T0,T1,TRet](CallSite site, T0 arg0, T1 arg1)
2017-07-26T11:53:32.4385116Z ##[error]   at System.Management.Automation.Interpreter.DynamicInstruction`3.Run(InterpretedFrame frame)
2017-07-26T11:53:32.4385116Z ##[error]   at System.Management.Automation.Interpreter.EnterTryCatchFinallyInstruction.Run(InterpretedFrame frame)

i never used this FindServicePoint and also can't find it in my test-project and i haven't any relative URI.

thanks for every help