form_error not displayed

Actually I pass some default datas with method "create()". This method use a model to pass some database datas to the view with the form.

I could put that part of the code in the same method called "add()" but I wanted to separate those two things.

I can resume my code as follow considering a user is filling the form :

1. A user fills the form and push "valider" button, the controller and action called are "devis/add".
   
2. In "devis/add", according to rules of validation we look if there are errors or not.
   
3. If there are some, We are taken to a method called "create()" which is gonna load the view with the form passing some datas needed to display form fields (<option> of <select> tag are generated this way). This is the same method called initialy to get the page with the form.
   
4. If there a no errors, the user is taken to a success page.