Usually such problems (Finding DCs, including Replication and
and Authentication) are related to DNS.
DNS
1) Dynamic for the zone supporting AD
2) All internal DNS client NIC\IP properties must specify SOLELY
that internal, dynamic DNS server (set.)
3) DCs and even DNS servers are DNS clients too -- see #2
Restart NetLogon on any DC if you change any of the above that
affects a DC.
It is no problem to re-transfer the roles if the DNS is setup correctly
and if you truly TRANSFERED them the first time -- if you SEIZED
them previously you must destroy the DC that use to hold them (you
can leave the OS installed but must "cycle DCPromo" to remove
and (optionally) re-add the DC there.