unable to register (Code d'erreur HTTP 401)

when i run subscription manager for first time the system give an uuid to the host and i can see it in the redhat customer portal but i can't see last check in, and when i run subscription-manager auto-attach or register second time i get :
Code d'erreur HTTP 401: Unable to make a connection using SSL client certificate.Please review proxy configuration and connectivity.

the system is behind a proxy, date and time are syncronized

any tips ?