ubuntu 16.04 wireless doesn't show available networks

I am having a latest HP Pavilion All-in-one desktop with Windows 10 OS. I added Ubuntu16 along side and was able to use wired network in both OS'es.

But when I wanted to connect my PC to a wireless network, I see that the the network menu doesn't list available networks, so I can choose one of them to connect. The same thing works correctly when I boot into windows. So, I cannot suspect that the PC doesn't have wireless support. It seems to be a problem of (probably) wireless drivers not being available.

I followed the instructions available here (https://askubuntu.com/questions/55868/installing-broadcom-wireless-drivers) to install broadcom drivers. Even after that I am unable to see the list of available networks.

As a next step, I added a wifi network using the internet connection dialog, by providing ssid, password etc. But still it didn't connect.

I am wondering what it takes to enable the system to show available networks and/or connect to a specific wifi network.

Thanks in advance for helping me out on this.