Yes I know there have been a number of posts about this but I have tried all the proposed solutions to no avail.

1st my configuration: advanced micro devices Inc Radeon HD6400M/7400M series [1002:6760] (prog-if 00 [vga controller]
Subsystem hp 6470M
Kernel modules: Radeon
No driver listed under lshw (never has)
Plasma version 4:5.12.7-ubuntu0.1
OS build: 4.4.0-148-generic
Xorg server 2:1.19.6

Now what I have tried and the results:
Grub update nomodset - no change
AMDGPU open source drivers with Mesa ppa - no change
AMDGPU pro drivers - no change
Xorg log shows a fatal server error. Warning (EE) error, NI not implemented
Tty2 sudo startx - unable to connect to Server: connection refused. Timeout in locking authority file ....

I have tried to install the AMD proprietary driver and open source driver to no avail. This is a clean upgrade to 18.04 through 16.04 from 14.04. the last display that worked was 14.04.

Any direction on where to look for solutions would be greatly appreciated.