class Devise::FailureApp

def self.default_url_options(*args)

so only the class-level attribute is used.
ApplicationController). Instance methods are not supported at the moment,
Try retrieving the URL options from the parent controller (usually 
def self.default_url_options(*args)
  if defined?(Devise.parent_controller.constantize)
    Devise.parent_controller.constantize.try(:default_url_options) || {}
  else
    {}
  end
end