Here’s my personal notes on restoring a Ubuntu (or other linux distro) wifi connection that has gone missing. Maybe they’ll be useful to you too.
Sometimes when Ubuntu comes out of suspend or even after booting from power-on the wifi connection disappears. Usually the little triangular wedge on the task bar is empty. Usually this is easy to fix.
If you click on the wedge, instead of seeing a wifi connection (or indeed any connections!) the menu just indicates that Ubuntu cannot see any available wifi connection.
In this case the most likely reason is that the network manager has crashed. We need to reboot it and we can do this on the fly without having to reboot the whole system
Open a command prompt (ctrl + Alt +t)
The on the command line in the console window that opens type:
sudo service network-manager restart
Enter your password when prompted and the network manager will be restarted.
Hopefully that should fix it.