I do see the many posts about this problem and I apologize for that.
The plugins server does go down from time to time. It doesn’t have a fallback because I’m trying to keep hosting costs down.
The plugins page should be up and running. If you’re still unable to install plugins, please double check that the firewall isn’t getting in the way.
Going forward, let me try and add a status page so that you could verify in real-time if the problem is with the plugins server.