Solved, thank you.
I tried to install on a brand new 2021 Dell XPS notebook at its full 1920 by 1200 resolution, but got only a blank activation box.
No problem at 800 by 600.
I previously had no problem installing on an older Huawei Matebook X Pro at 3000 x 2000 resolution and a 200% scale setting. Same install package, same validation code.
(I did not try changing the Dell 125% scale setting, BTW)
