Windows 10 update cannot connect (behind a firewall)

Question

Why cannot Windows 10 Update connect to its update servers even though there is a working internet connectivity?

About my setup

• running Windows 10 on a PC behind a dedicated firewall (pfsense 2.2.5)
• there is internet connectivity, port 80 / 443 works fine for anything else
• connecting the Windows 10 PC directly to my IPS's modem allows to update Windows 10 => suggests that the firewall is causing the problem

Already checked

• pfsense forum with the result that Windows 10 update should work without any hick-ups (not running any proxy)
• found and tried the resolutions mentioned in the MS Support article Can't download updates from Windows Update from behind a firewall or proxy server

Still, Windows 10 (version 1511) cannot update itself when I run it behind my firewall.

Any other suggestions/ideas?

Answer 1

Answering my own question.

I found the Windows Update Troubleshooter for Win10 from MS.

While running it, it in fact found and fixed a problem. After that, my Windows 10 can update itself now (great).

So, even though everything suggested a problem with my pfSense firewall it was some problem with the Windows Update itself.