The client calls the auth server.  If there isn't anything in
/sys/log/auth then the client isn't even trying the auth server.
It seems like the auth server doesn't know where the auth server
is, so to speak.

On the auth server, do

% ndb/csquery
> net!$auth!ticket

If there isn't a translation, that's the problem.  There are two
places you can specify the auth server, /net/ndb (plan 9 DHCP supplies
it) or in /lib/ndb/local.  Look for 'auth='.