Sometime Emacs won't connect on windows machines to https site.

This means you can't update packages from melpa or marmalade.

In this reddit thread the issue is describe with useful tips.

(url-retrieve
 "https://www.google.com"
 (lambda (status &rest args)
   (pop-to-buffer (current-buffer))))

The thread is expanded into instruction on marmalade: https://marmalade-repo.org/#windowsinstructions For me, the dlls in the latest of the sourceforge project failed. I used an altyernative source for the dlls files.

Copy all dlls from ftp://ftp.gnutls.org/gcrypt/gnutls/w32/ File: gnutls-3.5.8-w64.zip into a Emacs-25.1 `/bin` directory