[Samba] Join Domain error - the ubiquitous "specified domain does not exists or could not be contacted"

[Markb]

Existing Samba 4 network trying to added a new Windows 10 workstation. 
Getting the  "specified domain does not exists or could not be 
contacted" error.
Samba: Version 4.1.9-Zentyal
Samba as Primary Domain Controller  - simple file sharing
Server name:  APPSERVER1.local
Domain Name: LINGROUP
Win 10 updated to all latest.  SMB1 added in Windows Features

Ipconfig on workstation looks correct  (same server is DNS and DHCP 
server) except "DNS SUFFIX Serach List" does not included the domain 
"LINGROUP".  (Not sure if that only happens after joining domain or not.)
I can manually browse to the server in Explorer and see the server 
shares and user's home folder (browse to \\APPSERVER1) but the server 
does not show up in the network neighborhood.  Some, but not all, of the 
workstations do, and one time the backup server showed up but then went 
away.
I can ping the server by IP or name APPSERVER or APPSERVER.local (I 
realize .local is outdated).

I'm not seeing any DNS issues on the server.
I am NOT an admin but have used Samba in this small office environment 
for 15+ years so I know enough to be dangerous.  Any advice on where to 
start troubleshooting?

Pertinent Global settings:

[global]

admin users = sysadmin

name resolve order = wins lmhosts hosts bcast
	dns proxy = yes
#mcb
  wins support = yes

    dns proxy = no


force create mode = 0770
force directory mode = 0770
create mask = 0660

hosts allow = 127.0.0.1 192.168.1. 10.10.10. 192.168.2.
hosts deny = 0.0.0.0/0



#### Networking ####
#AND mask interfaces = 127.0.0.0/8 ens160 lo

    bind interfaces only = yes

  # force use of SMB1, Paradox database requires smb1
    server max protocol = NT1


#### Debugging/Accounting ####
    log file = /var/log/samba/log.%m
    max log size = 1000
    syslog = 0
   log level = 3

    panic action = /usr/share/samba/panic-action %d

    server role = classic primary domain controller
    passdb backend = tdbsam

    obey pam restrictions = yes
    unix password sync = yes
    passwd program = /usr/bin/passwd %u
    passwd chat = *Enter\snew\s*\spassword:* %n\n 
*Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* .
    pam password change = yes
    map to guest = bad user

   security = user




########## Domains ###########

workgroup = LINGROUP


server string = APP Samba %v %h
  # For Windows 10 client support, uncomment the following line:
server max protocol = NT1

domain logons = yes
domain master = yes
local master = yes
preferred master = yes