NetworkManager not showing or connecting to wi-fi networks

[NoOp]

On 08/14/2014 05:59 AM, Adam Funk wrote:
> Hi,
> 
> My son's laptop, which worked fine yesterday (& was left on but
> suspended overnight, as usual) has a weird problem today.  In the
> lightdm screen & when logged in, the NetworkManager applet doesn't
> list any wi-fi connections (there should be at least 1, sometimes 2,
> where it's sitting --- wi-fi is working fine on other computers in the
> same room), and when we try the "Connect to Hidden Wi-Fi Network"
> option & select the one in this house, the applet lines go up & down
> for a minute, then it fails to connect.
> 
> It's hard to get diagnostic information off that machine since it
> isn't networked, but if there's something specific I should look for,
> I can try.
> 
> I used lshw -C network and lsmod to check that the right driver is
> loaded, them tried rmmod & modprobe to reload it: same problem.  I
> tried sudo ifconfig, ifdown -a, ifup -a, and several reboots: no
> success.


This happens to me on occassion... but it always works on reboot.
Without rebooting, I've found that killing NetworkManager (note the
caps) and allowing it to restart usually fixes the problem for me. Example:

$ ps -e | grep Net
 7898 ?        00:00:00 NetworkManager
$ sudo kill 7898
NetworkManager should restart:
$ ps -e | grep Net
 8298 ?        00:00:00 NetworkManager


Make sure the wifi is not soft or hard blocked:
$ rfkill list
0: phy0: Wireless LAN
	Soft blocked: no
	Hard blocked: no

You don't mention which version of Ubuntu or which desktop version, so...
<https://help.ubuntu.com/community/WifiDocs/WirelessTroubleShootingGuide>