[Samba] RPC server unavailable?

[jimc]

I have a Samba 4.1.6 up and running(?)
When I try to join the AD, I get 'RPC server is unabailable.'
This also happens when I try the Microsoft Remote Administration tools, 
I get the same issue.
The samba, smbd, and auth logs don't seem to provide the answer I need, 
but that may only mean I can't see it.
The workgroup server works fine.
I have spent hours online and in the samba lists archives and have not 
been able to find the answer.
I have been through the whole how-to again and everything checks.
What am I missing this time?
Thanks!

-jimc