Ethercable unplugged after Yosemite upgrade

HI, since upgrading (?) to Yosemite, in Network under Preferences, it indicates the Ethernet Cable is unplugged. So I can only use wifi connection, although the cable works fine (tested) and provides the signal. Have looked at different posts, could not find a solution yet. I would really prefer to use the ethernet connection for security reasons. Is there a fix? Thanks!