Allegedly, on or about 17 May 2017, Lucélio Gomes de Freitas sent:
Old "Fedora 20-x86_64" installed and working. Due to a problem, I Changed my motherboard and lost network(Internet) connection. How to recover connection before install Fedora-Kde-live-25-1-3?
Chances are that your previous network connected was associated with the hardware on your old motherboard (rather than being generic networking settings that will work with any network adaptor), and since it's not there, it doesn't fire up.
You could just delete your network configuration, and create a new one. Unless your network has special configuration, the chances are that a new one ought to get created that will simply work.