Q: fail to log in imessage on macbook pro

I can't log in imessage and facetime!! Since I updated osx to yosemite last year, whenever I try to log in to imessage, it shows "Could not sign in. Please check your network connection and try again", and if I try to log in facetime, it does nothing. I tries lots of solution including changing network, vpn, modifying host file, using third party package like hackintosh, but none of these work. Even though I ask customer support service for help, the problem is still there. I use macbook pro retina 13inch 2013, yosemite 10.10.1 Could someone help me? Any help would be appreciated.