After a world update I couldn’t start my wlan-device. I always got:

„Operation not possible due to RF-kill“

I did:

# rfkill list

0: phy0: Wireless LAN
    Soft blocked: no
    Hard blocked: yes

But I wasn’t able to unblock my device from the command line using rfkill unblock 0.
After a while I figured out that updating conman (to version 1.15) changed /var/lib/connman/settings like this:

[WiFi]
Enable=false

I set it to true and it worked again:)