flash[:notice] not showing after reset_session

I've seen a post suggesting the flash variable is also cleared when the session is reset, but haven't managed to find any suggestions on what to do to get this to work..

I am using 2 filters (prepare_session, then login_required) before processing an action.
But my session has expired (as expected), so instead of seeing the view associated with my action, I am redirected to my login page, which should display my flash[:notice] variable, but I am not seeing it. I do however, see the flash[:notice] for this same situation but where the session hasn't expired (when user is not logged in).

Would really appreciate some help!
thanks, Serena.

  def prepare_session
    creation_time = session[:creation_time] || Time.now
    if !session[:expiry_time].nil? and session[:expiry_time] < Time.now
      #Session has expired. Clear the current user from the session
      reset_session
    end
   
    # Assign a new expiry time, whether the session has expired or not
    session[:expiry_time] = MAX_SESSION_TIME.seconds.from_now
   
    return true
  end
 
  def login_required
    unless session[:account].nil?
      return true
    end
    flash[:notice] = "You are not logged in"
    redirect_to :action => "login"
    return false
  end