This has been driving me nuts. Here is a sequence of events that happened (to the best of my memory):
Wifi was working fine on my Ubuntu 16.04 computer. But after installing security updates (using unattended-upgrade), somehow the network manager could not detect any Wifi. I tried rebooting the system, then the network manager showed "device not managed" for both Ethernet and Wireless connections. According to this thread and many alike, I modified
/etc/NetworkManager/NetworkManager.conf
and changed the managed=false to managed=true, and then restarted the network-manager service. This did make the "device not managed" go away, and I did see the list of Wifi's in the drop-down menu of network manager. However, when I tried to connect to any one of them, the network manager just waited for a while and eventually failed to connect. It was almost as if those listed Wifi names are fake.
I then tried to use the command-line tool nmcli and see if there is any useful error messages. Notice that all this time managed=true is set. First, I ran
nmcli device wifi list
and I see a list of wifi spots that seemed pretty normal. Then I tried
nmcli device wifi connect <SSID> password <PASSWORD>
with SSID and PASSWORD being the wifi spot I'm trying to connect to. Then, after a few seconds wait, an error shows up:
Error: Connection activation failed: (53) The Wi-Fi network could not be found
Additional Question
Regarding the "device not managed" problem, it is strange to me that (1) it occurs at all (2) setting managed=true is the correct fix. I have checked the NetworkManager.conf files on several other 16.04 machines I have access to, and they all have managed=false and are still able to connect to the Internet. What's an explanation of this?
I sincerely appreciate your help!
