Samba 4 security = domain

hello, I need your help to integrate my Samba server in my Windows AD.

I succeeded to configure and to operate my samba in the version 3 and redhat 6 with security = domain.

But now I have to configure my samba in the version 4 on redhat 8 with security = domain too and not with ads, I don't want use kerberos.

When I want join my domain I have :

Failed to join domain: failed to find DC for domain 'Mydomain' - {Operation Failed} The requested operation was un successful.

I will link my smb.conf and my nsswitch.