Can not identify members on protected pages

I’m a new user who discovers Grav. I use Skeleton Landio.
I have created a new page that I want to make accessible only to registered members:

title: 'titre de la page'
    site.login: true

Access to this page send me well to the login form:
Screenshot-2017-10-11 User Login SNTU-CFDT Orléans
but access is unrecognized, why?
Yet the file \www\grav-landio\user\accounts\nicolas.yaml exist
Can you help me (sorry I use Google translate)