Try to see if you can get the new list of software. Start yast2, and go to Software Add/Remove. See if that will start, or if you get the same error.
Find out what repo you are using, and see if that server is active by a ping command:
ping -c 1 <ip address of server>
ping -c 1 <url of server>
Check network settings. Check logs such as /var/log/messages and dmesg.