Our server is surely online but, you are not really connecting there (if users could connect to our server directly, it would go down in minutes because of the load), you connect through Cloudflare so, it's possible your local node might have issues.
Also, yesterday flightsim.to went down for some users, and it also turned out to be a Cloudflare shortage.
If the issue is localized to your local node, you might try with a VPN, which will connect to a different one, but these issues usually sort themselves out automatically in a very short time, so I'm sure it will eventually work.
I assuming that, in addition to having configured the antivirus correctly, you don't have a firewall that is blocking the installer from going online.