Cannot access docker webserver from external machine

I am trying to access a website running under docker.

If I bring the container up under Linux, then I can access the site via localhost or the machine name or DynDns from another machine on the network / internet.

If I bring up the same container on Docker Desktop for Windows, I can access it via localhost, but not from an external machine. I have opened ports 80 and 443 on the Windows machine.

How can I fix this?

Windows 10 / WSL2