Windows 10 Upgrade Problem

I'm a developer, mostly C++ but I need to maintain some VB6 programs so I have the VB6 development environment installed. I haven't upgraded up to now Win 10 because of this.

However customers have run into run into problems with Win 10 2004 so I need to upgrade at least one computer to Win 10 to test. I've run into the same problem on two computers now.

First I tried cloning the Windows drive on my development computer (Win 7 x64) , setting up a dual boot, and upgrading one of the installations. I was installing Win 10 1909 Sept 2020 build.  After install the screen came up blank. I tried Ctrl+Alt+Del with no effect. I also tried Windows key + Ctrl + Shift + B. Neither did anything.

I rolled back to Win 7 on that computer and tried another computer.

The other computer was running Win 7 x86.  This had the same problem.  I came across another solution which was to boot into safe mode and look at the Registry, but hitting F8 did nothing.

I watched the process more closely on the second computer.  After the upgrade, the screen was just blank.  I shut off the computer and restarted.  It had the spinning dots for a bit, then said something along the lines of "Attempting to fix install..." and then it rebooted.  On the second boot the dots spin for a while and it goes to a blank screen and refuses to respond to any input. 

On the next shut down and restart it rolls back to Win 7.

The video hardware is different on the two computers.  The first has two Nvidia video cards and the second has one that I think is Intel video.  The second computer has only a minimal number of peripherals installed.

Is there any way to get this to boot right?