So I think I "may" have fixed it. I upped the logging level in Samba and noticed that it was a NTLM auth problem.
So I added ntlm auth = yes which allows NTLMv1 clients to connect in the smb.conf file.
SAMBA 4.5 changed the default method of NTLM to NTLMv2 clients only. Older clients that don't use NTLMv2 can't connect without changing this setting.
What a PITA that was to diagnose.
(https://www.samba.org/samba/docs/current/man-html/smb.conf.5.html)