When installing Ubuntu, and during install You choose to use wlan0 interface.
On first system boot wireless becomes unmanaged, and You can’t choose wireless AP.
solution is to edit file /etc/network/interfaces
There should be lines like
auto wlan0 iface wlan0 inet dhcp wpa-ssid wifi-name wpa-psk wifi-key
delete those lines and reboot computer. Network manager will be able to control wifi.