[Samba] Roaming profiles don't work properly on newly joined Windows clients

[Piers Kittel]

Hi all,

We're a small charity and we've got a working and stable Debian 9 AD 
system using one Samba server (version 4.9.5-Debian) and 4 x Windows 10 
Pro clients.  The server has two shared folders - "Profiles" for roaming 
profiles and "users" for user's home directories. We've just got 
delivery of two donated computers, and we got 2 new staff members.  I 
wiped the new computers, reinstalled Windows 10 Pro to build 1903, and 
connected them both to the AD server, they both connected to the domain 
fine.  I set up the account for the new staff member fine, and when I 
logged on to her new account, I immediately got the message that was 
something like "We couldn't set up the profile, so we've started a 
temporary profile which will be deleted on log-off".  While logged on as 
the new user, I'm able to create folders in both shares - 
\\192.168.0.17\Profiles and \\192.168.0.17\users fine.  I'm able to log 
on into my own existing profile, everything loaded fine, but when I 
logged off, I got something like "Unable to synchronize your profile to 
the server".

I checked the computers we already are using and they work fine with the 
new and existing users and they have already upgraded themselves to 
build 1903 - it's only the new, recently joined computers that are 
unable to write profiles of existing and new users to the server.  
Everything else works fine - I'm able to manage the server using the 
RSAT, logon & logoff fine, everything - just can't write profile to the 
server.

I've followed the instructions on the Samba wiki with a fine toothcomb 
and can't find what I've missed - I'm sure it's something simple - I'm 
really hoping someone can tell me what I'm doing wrong?

Advice greatly appreciated in advance!

With kind regards - Piers