Hi!
I'm trying to reassign the actor of an approval process and I'm getting that error : INSUFFICIENT_ACCESS_ON_CROSS_REFERENCE_ENTITY


This is the main code:
try{

  Approval.ProcessResult result=AprobacionHelper.aprobarOportunidad(op, obs); 
 
  System.debug('resultado de la aprobación ========>' +result);
 
  Reasignacion__c r = AprobacionHelper.recuperaAprobadorReasignadas(op.Id);
  if (r!=null){
  
   List<Id> newWorkItemIds= result.getNewWorkitemIds();
    ///
    // First, get the ID of the newly created item

   List<Id> nwii = result.getNewWorkitemIds();
    ///
         AprobacionHelper.reasignar(nwii, r);
  }
           }catch(Exception e)

And the methods:

public static Approval.ProcessResult aprobarOportunidad(Opportunity op,Observaciones__c obs){


  Approval.ProcessSubmitRequest req1 = new Approval.ProcessSubmitRequest();

        req1.setComments(obs.Observacion__c);
        req1.setObjectId(op.Id);       
        // Submit the approval request for the account
        Approval.ProcessResult result = Approval.process(req1);
        return result;
 }

public static void reasignar(List<Id>newWorkItemIds,Reasignacion__c r){
   Approval.ProcessWorkitemRequest req2 = new Approval.ProcessWorkitemRequest();
  req2.setComments(r.Comentarios__c);
  req2.setAction('Approve');
  req2.setNextApproverIds(new Id[] {r.aprobador__c});
  req2.setWorkitemId(newWorkItemIds.get(0));
  Approval.ProcessResult result2 = Approval.process(req2);

  }
And there I got following error message:
10:35:11.596 (596521000)|EXCEPTION_THROWN|[57]|System.DmlException: Process failed. First exception on row 0; first error: INSUFFICIENT_ACCESS_ON_CROSS_REFERENCE_ENTITY, insufficient access rights on cross-reference id: []
10:35:11.597 (597507000)|SYSTEM_METHOD_EXIT|[57]|Approval.process(Approval.ProcessRequest)