Can't use setActiveStage js-function

Hi!

I have created simple example (set this function onLoad form):

function test() {

var procid=Xrm.Page.getAttribute("processid").getValue();
if (procid=="9f032107-53b0-490b-b178-43ca28e42ec4")
{
  var stcopy = Xrm.Page.data.entity.attributes.get("elko_stageid").getValue();
  var GUID = "";
  if (stcopy="5705561b-ded6-47b9-a273-25932a264f1d")
  {
   GUID="fbef4b74-ec42-4a27-92a6-d683ca2a31d5";
   Xrm.Page.data.process.setActiveStage(GUID,
                                    function () {
                                        //no event
                                    });
  }

}

}

But I always getting an error - "Invalid".

There are three reasons why this value may be returned:

• The stageId parameter is a non-existent stage ID value.

• The active stage isn’t the selected stage

• The record hasn’t been saved yet.

Have anybody some ideas to solve it? 

Thanks!