I have a reverse proxy with SSL configured and working (showing a valid and correct certificate), however it isn't loading the actual webpage.
I have a vhost on the proxy configured for port 80 and that loads the content no problem, however over 443, I get to the sites default Apache test page.
My question is does the site that the Reverse Proxy is directing to need to be listening on 443? I assume I don't need the actual certificate installed on that site, only on the proxy, but does it need to listen on 443?
Port 443 is the default port for HTTPS connection. It would be recommended leaving in on that port, but you don't have to if there is an issue. You can either add the port to your URL somepage.com:port which is rather silly. Or you can catch all the requests coming in on port 443 and redirect them to the desired port. Keep in mind that port 80 is reserved for HTTP, not HTTPS.