SAMBA stopped syncing with LDAP NT_STATUS_CONNECTION_REFUSED

Hello,

Our server stopped syncing OPENLDAP with SAMBA4 for no apparent reason.

The error is:
Failed to connect to ldap URL ‘ldaps://ucs1.domain.lan’ - LDAP client internal error: NT_STATUS_CONNECTION_REFUSED
Failed to connect to ‘ldaps://ucs1.domain.lan’ with backend ‘ldaps’: LDAP client internal error: NT_STATUS_CONNECTION_REFUSED
Failed to connect to ldaps://ucs1.domain.lan - LDAP client internal error: NT_STATUS_CONNECTION_REFUSED

They both are working OK (SAMBA works and LDAP works) but don’t sync info between them.
For example, a created group on UCS (LDAP) won’t appear on SAMBA and vice-versa.

Any pointers on how to fix this?

Thanks!