root@kali:~# ifconfig wlan0 down

root@kali:~# airmon-ng check kill

Killing these processes:

PID Name

1508 wpa_supplicant

root@kali:~# iwconfig wlan0 mode monitor

Error for wireless request “Set Mode” (8B06) :

SET failed on device wlan0 ; Operation not permitted.

root@kali:~# ifconfig wlan0 up

SIOCSIFFLAGS: Operation not possible due to RF-kill

root@kali:~#

I ended up installing a fresh install of kali instead of the custom one from Zaid, everything works good.