I’m using Ubuntu 14.04.1 server. Recently, I installed Ubuntu desktop for it; before that it had automatically gained an IP address through DHCP. After installing Ubuntu desktop, I have provided an IP address as static but it is not obtaining that IP address. Instead, it is showing the DHCP address. When I check connection information, it is showing me the error message, “Error displaying connection information, no valid active connection found.” I tried with ifconfig command but it shows the IP address as gained by DHCP but not the static one which I gave so I can browse the internet. I need to provide a static IP address. I have uploaded the error image. Please help me.

Source: network manager not working – Ask Ubuntu