Sucuri Firewall only proxy traffic going over port 80 (HTTP) and 443 (HTTPS).

If your application runs in a different port, you should either: a) create a sub-domain pointing directly to your Hosting IP; or b) proxy the application port, from the server side, to port 80 or 443.

For example, if you run Jenkins, which listens on port 8080 by default, you can proxy with NGINX or HAProxy for example:

Unfortunately, our team can't help you setup this proxy on the server side, but your sysadmin or hosting provider should be able to help you through this process.

You can read more about reverse proxies here and here.