We struggled with this for a long time because you need to do two things to make it work.
1. Whitelist the IP address in the Virtual Proxy (which you've done) and
2. Allow HTTP / port 80 in the Proxy configuration. Note, you don't even need to allow port 80 through the firewall. If you point to address https://nnn.nnn.nnn.nnn/hub then there will be no traffic on port 80, it's 100% HTTPS on 443.
Note: this is for Qlik Sense 2.02
Screen shot of our proxy configuration page below.