I have a WordPress installation on a Windows Server that we manage. One issue that we've come across is that if you click the Update button on a plugin, the in-progress icon spins, but the update never completes.
I found that the updates were actually downloading to Windows/Temp dir but never got beyond zero bytes. In wp-config, I changed the destination of the downloads to a local dir:
define( 'WP_TEMP_DIR', ABSPATH . 'wp-content/tmp/') ;
...which worked -- except that the downloads are still not getting past creating the zero byte file. So it's not a permission issue as far as I can see, since the file is created (advanced-custom-fields.4.4.3.tmp for example).
It just never actually downloads.
Any ideas? Is this a CURL issue? FTP? I'm not sure what mechanism WordPress uses to download the update files behind the scenes.
Thanks!
Going to answer my own item today. It turns out that the server was going through a firewall that was inspecting the SSL packets, and substituting its own Fortigate certificate instead of the websites - which invalidated the secure connection. In this case www.wordpress.org was the site being "blocked" due to the insecure connection. We fixed the firewall, and plugin updates could then download properly.