Since 2 days ago I can't edit any connections using network manager, because the "edit" button is greyed out. I tried doing a normal restart of the service to no avail.
One quick work-around is to invoke the connection editor manually from the command line:
You'll get the same familiar edit screen. Worked for me.
Try this fix-for-error-network-device-not i think you got the similar problem as me.
Summary from linked content:
Run in terminal
sudo /etc/init.d/networking restart
sudo killall NetworkManager
Now attempt to configure your interface.
For NetworkManager to manage an interface, that interface must not be configured under /etc/network/interfaces. Following is my /etc/network/interfaces:
[ubuntu@desktop network] cat interfaces # This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # The loopback network interface auto lo iface lo inet loopback
Notice that eth0 does not show up; it is managed by NetworkManager. And because of this, it can now be edited with nm-connection-editor, the GUI.
Of course, NetworkManager must be configured to manage your eth0 connection. Follow Sumant's solution on this page on how to configure managed=true (I am not copying his answer because I want to respect his and give credit to where it is due).
After setting up a bridge (e.g. here) the name manager does not show the enslaved interfaces under the 'Ethernet' tab. This is probably normal' yet the "edit connections" turns gray.
This graying out is probably a bug.
Fortunately the actual functionality oft network manager seems to work so you can run nm-connection-editor from the command line to edit the connections using gui or use the command line tool nmcli.
For example to list your connections try:
nmcli con show
It is probably because you did not choose a certificate in the "Wi-Fi Security tab". If you don't have one, mark the checkbox "No CA certificate is required".
u might need to unlock it, there might be an unlock button somweher in that window, if u cant find it try maximising the window and look for it, happened to me once :)