Visual Studio 2019 + IIS Express 10 "Cert refused error" (won't run TLS 1.2)

Installed VS2019 on Windows 7. Created ASP.NET web application from template. Do nothing. Run project "IIS Express + FireFox" Get message about installing development certificate and running site under HTTPS Accept certificate and IIS starts site on https://localhost:43315

Get error from browser Error code: SSL_ERROR_UNSUPPORTED_VERSION

Switching to Edge, I get NET::ERR_SSL_OBSOLETE_VERSION

Have tried :

https://docs.microsoft.com/en-us/mem/configmgr/core/plan-design/security/enable-tls-1-2-troubleshoot

https://docs.microsoft.com/en-us/mem/configmgr/core/plan-design/security/enable-tls-1-2-client

https://support.microsoft.com/en-gb/help/3140245/update-to-enable-tls-1-1-and-tls-1-2-as-default-secure-protocols-in-wi

https://www.pluralsight.com/guides/visual-studio-2017-resolving-ssl-tls-connections-problems-with-iis-express

But have had no luck.

So as far as I can see:

1. I have a cert
2. The site is running on the right port range
3. Checking all the registry values (and many reboots) suggests TLS 1.2 is available.

so what's wrong ?

Thanks in advance all.