Ubuntu – Wifi doesn’t work on ubuntu

I installed Ubuntu on my Dell laptop, but the wifi isn't working! I tried to solve the problem using different commands suggested by people on this forum, but none of them worked for me!

When I ran rfkill list all I get the following:

$ rfkill unblock all
$ rfkill list all
0 : dell-wifi: Wireless LAN
        Soft blocked: no
        Hard blocked: yes
0 : phy0: Wireless LAN
        Soft blocked: no
        Hard blocked: no
$ sudo rfkill unblock wifi      
$ rfkill list all
0 : dell-wifi: Wireless LAN
        Soft blocked: no
        Hard blocked: yes
0 : phy0: Wireless LAN
        Soft blocked: no
        Hard blocked: no

When I saw that there is a problem with the hardware, I checked the BIOS and everything was set correctly!