Can't connect to Minecraft Server

Me and some friends have been playing FTB infinity evolved on Minecraft for a few weeks now but out of nowhere today it doesn't allow anyone to connect to play. We all keep getting the message "java.net.ConnectionException: Connection refused: no further information:" I've tried restarting the server, or just stopping and starting the server and it doesn't change. I've looked through all the logs and options on nitrado and can't seem to find any reason. Help?