When you installed Qlik Sense you had the option to pick a hostname.
Most likely that would have been the machine name and not the IP.
So you can either access the server by it's machine name OR you can add your servers IP to the proxy white list.
You can find the white list by going to the proxy configuration in the QMC and then enable the advanced settings in the right hand side panel.
The whitelist controls which servers/origins are allowed to open a websocket connection to the Qlik Sense server.