I think I will give up and wait a year for a newer build. I have done all I can and thanks again to everyone.
I eventually did the following based on the links below and… same again. I did hear it could be because my PC has two GPUs but not my fault 
So-
I uninstalled Darktable.
Scanned the C drive for Darktable and it found files and folder, I deleted them all as suggested here.I can't get Darktable to work anymore - #20 by kofa
Did a reset and scannow Using System File Checker in Windows - Microsoft Support
Reinstalled newly downloaded Darktable and failed again.
No PC brain sergery I have a 5 month old PC with latest Windows and Intel chip, if that’s not good enough then I give up.
I seem to recall I could (video editor) decide to use / not use the second GPU. The Nvidia GPU has a control panel that makes no sense to me, may to a gamer ? So will try maybe but not that important.