Well, I activated debug_log=6 in sssd.conf
I added ad_gpo_access_control = disabled in domain section
and users loging is restablished.
In fedora 22, ad_gpo_access_control was not necessary to enable loging.
This should be added to the tutorial
https://fedorahosted.org/sssd/wiki/Configuring_sssd_with_ad_server
Best Regards,
Ed