[Samba] Replication error on newly joined DC

[Peter Pollock]

OK. I have been trying to add a DC. I've followed the instructions to build
a DC that are on the Samba Wiki, (
https://wiki.samba.org/index.php/Joining_a_Samba_DC_to_an_Existing_Active_Directory)
bouncing around all the links to install and configure Bind9.

I've built it on ubuntu 22.04 Jammy with the addition of the repos from
Michael Tokarev. I've started Samba..... and it errors out on replication:

 itadmin at dc05:/etc$ sudo samba-tool drs showrepl
Global parameter server services found in service section!
ERROR(<class 'samba.drs_utils.drsException'>): DRS connection to
dc05.internal.mydomain failed - drsException: DRS connection to
dc05.internal.mydomain failed: (3221226038, 'The transport-connection
attempt was refused by the remote system.')

Can anyone suggest where I go from here please?