Seems the same problem I've had.
Solution was:
/etc/NetworkManager/NetworkManager.conf
Content of the file:
[main]
plugins=ifupdown,keyfile
[ifupdown]
managed=true
After upgrade from Wheezy to Jessie managed=false; set it to TRUE and
Network-connection will not fail anymore
In my <control-bar> at the bottom of the screen, i have applet
networkmanagement installed - before correcting above mentioned file, it
always showed that NO network-connection is available.
A workaround was "ifup eth0" in a console-window; that caused
software-management (in systemsettings) not to fail in case of beeing
'offline'.
Greetings Herbert
--
Der Horizont vieler Menschen ist ein Kreis mit Radius Null
- und das nennen sie ihren Standpunkt