if your WLAN option is greyed out on your network manager, run these commands, you will likely get this output:

rfkill list all
0: phy0: Wireless LAN
	Soft blocked: no
	Hard blocked: yes
1: hci0: Bluetooth
	Soft blocked: no

how to fix it:

1. check that WLAN is enabled in BIOS (it’s under “Advanced” right next to Bluetooth enabled/disabled)

2. open terminal become root and:

echo "wistron_btns" >> /etc/modules; # on older linux (like knoppix -> this worked for me)
echo "amilo-rfkill" >> /etc/modules; # on newer linux