Comment # 7 on bug 1107697 from Vadim Krevs

I get something very similar, often triggered after establishing a VPN
connection via Network Manager. 

Suddenly, the network manager applet in the systray vanishes. The only way to
bring it back is to "systemctl restart network NetworkManager". After the
restart, the network manager applet in the systray is back but curiously the
"wire" on the icon is blue. 

Once this happens, it is no longer possible to connect to the VPN. Only a
complete laptop reboot fixes this. 

This started happening after update to whatever snapshot was latest on Sep 1st
(but I was a couple of snapshots behind).