Do I need to do something to pass parameters between states in a Workflow? I have defined a workflow field... then in the first state I assign it a value, in the second state I want to use it but the value comes empty... why? (if I use a single state the parameters are as expected)

Yes as Jen said. If it’s a workflow field and not a state field it should be applicable to all states in the workflow

Thanks, will check it out