Thanks for the reply. I managed to resolved this by disabling the "Use automatic configuration script" option which was setup for my organization. Having a proxy server setup was fine, but something in the script was blocking either the QlikSense service or the 4848 port I guess.
Nothing was required to be tweaked on my firewall.
Go to QlikSense QMC -> Proxies.
1,Websocket origin White list - Add (Machine/ the Server running Qliksense server) name. if u want to use IP address instead of Machine name then add IP address,
2. Tick Allow HTTP
Restart QlikSense Proxy services in Services or restart your computer.
See the attachment
QMC Proxy Settings.png 49.7 K