I've remove ehternet cable, connected WiFi to my home router. Now I could reboot as much as I want, WiFi worked, checkbox is visible and is ON inside network manager widget.
BUT, later I disabled WiFi connection, attached etherne cable, rebooted and that's it - wlan0 device missing, no WiFi checkbox!
I did another experiment.
I've remove ehternet cable, connected WiFi to my home router. Now I could reboot as much as I want, WiFi worked, checkbox is visible and is ON inside network manager widget.
BUT, later I disabled WiFi connection, attached etherne cable, rebooted and that's it - wlan0 device missing, no WiFi checkbox!