Request not supported: SetStateRequest

I have a plugin on CRM 2016 online with this code to set the quote to active, but I receive the error 'Request not supported: SetStateRequest'.  Can anyone help me resolve this.  The plugin step is Update / Post-Operation / Synchronous.

SetStateRequest ActiveQuote = new SetStateRequest();

EntityReference ent = new EntityReference(postMessageImage.LogicalName, postMessageImage.Id);
ActiveQuote.EntityMoniker = ent;
ActiveQuote.State = new OptionSetValue(1);
ActiveQuote.Status = new OptionSetValue(3);
ActiveQuote.RequestName = "SetStateRequest";

SetStateResponse response = (SetStateResponse)service.Execute(ActiveQuote) ;