The problem seems to be that there is no error handling at nvda.pyw line 29, which calls setlocale with an empty string to set it to the system locale. If the system ends up being configured with an impossible setting such as en-nl this fails.
Hmm, I believe I have the same settings (display language and date/time format English UK, country the Netherlands. Still it seems to work fine here.
In the windows 10 language settings, what languages do you have available? Only English, or Dutch as well? Dutch is my default app language, while English is below Dutch in the list and is set as display language.
Here, English is the first in the list and set as default app language.
There are language packs installed for Ducht (Netherlands) and Dutch
If you look in the old language settings (Control panel, Region), you
can select a date/time/number format. This list seems to have way more
options than it had before. For example, English has variants like
Europe, Belgium, Netherlands etc. Choosing one of those uncommon
variants should trigger this. Please note that you might need to restart
for the changes to take effect.
This seems to have been what was preventing me from installing NVDA at all. When running the installer I get "an error has occured" right after the logo and this shows up in the log file (which gets deleted when the dialog is closed, btw, so this took me a while to hunt down):
Traceback (most recent call last):
File "nvda.pyw", line 29, in <module>
File "locale.pyo", line 581, in setlocale
locale.Error: unsupported locale setting
I'm in Germany, Windows is set to "English (Germany)". Switching to "English (United States)" allowed me to run the installer normally.