I have some problems with iCloud, safari, app store and iTunes after upgrading to Sierra. iCloud: cannot connect to the server. safari: I can open the safari but cannot browse any website, it always blank page, but I can use chrome to browse any pages. app store: I can open the app store but there is noting on it, looks like cannot connect to the server. iTunes: i can open the iTunes but there is nothing on it. It will crash after 1 minute. I have download the newest version from apple website but still not working. Anyone know what happened?