After upgrading to 2.73.1, attempts to use Invoke-WebRequest (Windows only) to download from the Jenkins server (basically any request...but in this case it was downloading the slave.jar file) always throw:

The request was aborted: Could not create SSL/TLS secure channel.

This server has https enabled, with http redirecting to https via nginx.  Nothing else changed except the upgrade from 2.60.3.

Now, this is quite possible a server configuration error, but I'm looking for some info on what might have caused the regression.

Connections of nodes via SSH, as well as curl on non-Windows platforms seem to be fine.  Running inside the browser on Windows seems to be fine too.