usermod and processes

[TrekkingBob]

Tried to simply add a new user. Can add user, and CLI login, but no GUI desktop login.

Fresh install xenial-mate-rock64-0.5.15-136-arm64.img.xz on SD card via Etcher on ubuntu 16.04

Boot to GUI login -> ctl-alt-f1 to terminal

Change sudo password:
Login as root -

Code:

sudo su

change password

Code:

passwd

set it
Adduser

Code:

adduser <nickname>

set password
set Full name - <Wholefirstname>
leave room/email/phone blank
reboot
GUI Login shows users: Rock64 and <Wholefirstname>
select <Wholefirstname>
use <nickname> password
reports: Incorrect password, please try again
And no combination of old and new user or root passwords work. Is there a step I am missing to simply add a user? Eventually I want Rock64 user replaced with my name, but keep the hostname as Rock64. I have tried changing the Rock64 user name as in previous posts, and now tried to add a user, and all with the same outcome (when commands and permissions done correctly) - Incorrect password, please try again