Update the active stage of Opportunity in the Business Process Flow

Hi,

as in the subject, I'm trying to update the active stage (Qualify, Propose, Contract, Close) of the opportunity in the BPF, i'm going in this way:

Entity updatedStage = new Entity("opportunity");
        updatedStage.Id = (Guid)id;   //Opportunty ID
        updatedStage["stageid"] = newActiveStageId;   //Active stage ID
        updatedStage["processid"] = processOpp1Id;     //Active process ID            
        crmSvc.Update(updatedStage);

I'm not getting any errors, but after refreshing the page, the values aren't saved.

Thanks for any help.