ActionController :: UnknownFormat in Devise :: SessionController # new in rails 4

I have been trying for a long time and did google about the problem, I cannot get rid of it. Can anyone please explain why this is happening and how to solve it.

  def new
    self.resource = resource_class.new(sign_in_params)
    clean_up_passwords(resource)
    respond_with(resource, serialize_options(resource))
  end

      

        
        
        
      

    

Error on line following response_with (resource, serialize_options (resource))

When I register the program, you will send a confirmation link. When I click on the link getting the above error and here is my url

http://localhost/users/sign_in.47

      

        
        
        
      

    

update 1

Here is my action show confirms_controller.rb

  def show
    self.resource = resource_class.confirm_by_token(params[:confirmation_token])
    yield resource if block_given?

    if resource.errors.empty?
      set_flash_message(:notice, :confirmed) if is_flashing_format?
      respond_with_navigational(resource){ redirect_to after_confirmation_path_for(resource_name, resource) }
    else
      respond_with_navigational(resource.errors, status: :unprocessable_entity){ render :new }
    end
  end

def after_sign_up_or_sign_in_path_for resource
      User.where(id: resource.id).update_all(online: true)
      dashboard_path
    end

      

        
        
        
      

    

I need to update the user as online as soon as they are logged in, so I used resource.id, which makes me worry.