Whatsapp Web QR code not loading on Chrome/Firefox on Ubuntu 14.04

I am trying to use the service https://web.whatsapp.com/ on Chrome/Firefox on Ubuntu 14.04 LTS (Dual boot Windows 8.1). But the QR code that needs to be scanned by the Whatsapp mobile app is not loading. QR code loads perfectly fine on Chrome on Windows 8.1 and others systems having Ubuntu, without any glitch.

I have tried re-installing both Chrome and Firefox from scratch, and both are in latest versions available.

What could be the possible reasons for this error and how can it be fixed?

Update: This is how it looks on Chrome: http://i.imgur.com/b5lI1WU.png
Chrome Version 41.0.2272.76 (64-bit):
Firefox 36.0
Ubuntu 14.04 LTS 64 bit

Solution 1:

If you are behind a proxy, it helps to remove the socks proxy configuration.

To do this in Ubuntu 16.04 (and if I remember correctly is exactly the same in Ubuntu 14.04), just go to "System Settings" -> "Network" -> "Proxy", and delete (left in blank) the socks server line and left port in 0.

You don't need to apply this -system wide-, just in the user you want to authenticate in Whatsapp Web.

Once you are done with Whatsapp Web Authentication, you can restore your previous socks proxy settings.