Hey all! My problem? Can't get into Messages on my Macbook (explained below). Authentication. This is killing me. It's driven me nuts since the beginning of October. I spend a solid 5-10 hours a week trying to fix it. Called Apple (they sent it to engineering and took a log of my computer when I start up messages). I never heard back and emailed the woman a few times. That was four weeks ago. Also went to the store, Dumbfounded. I used to work at The Apple store and I feel like we cared a lot more than these guys and gals. A guy like me would've never left until it worked. So, please, my family, lend me your support -- Fix my mac! Other people have this issue. A handful. They try all the normal tricks - GO! OS: Sierra 10.12.1 System: Macbook11,1 MacBook Pro (Retina, 15-inch, Late 2013) with a 2.3 GHz Intel Core i7 and 16 GB Ram. Issue: Messages produces "An error occurred during authentication." Facetime as well. This has been for over a mont. I am an Apple Store alumnus and when I went there with the issue, the Genius bar was dumbfounded. I called support. Support passed it to engineering. four weeks ago. This is a screenshot of the issue: http://i.imgur.com/wiMkMvq.png It's the System: It must be an issue with this system. I know this because I also have a Macbook late 2008 on the same network. On that computer I can log-in no problem. Another Apple ID I have also gets the same error on this system. Theory: My knowledge is limited in this area but I have a theory. I believe the ports that Apple uses to contact its authentication servers are being blocked locally. I simply do not know how to unblock them. More specifically, it seems the ports 53, 80, 443, 4080, 5223 need to be open for FaceTime and Messages. Both of these apps alert the "/etc/pf.conf" file to open the necessary ports while they are running. I believe that Messages and FaceTime are not able to do this. In other words, both apps rely on the same mechanism of opening the correct ports on the Macbook. This mechanism is failing, it seems. After running some scans I believe these ports are closed. And they probably ought to be until they are opened by an app to use them. The only things I can think of -- and I'm not sure if my memory is correct at all, is that I may have ended a process weeks ago that does this. Also, I may have used a command in terminal in an effort to try to turn off IPv6. I can't remember. This may also not be related. References: I relied heavily on these articles for information: This article written by Apple seems to suggest this: [URL='https://support.apple.com/en-us/HT202078[/url]']https://support.apple.com/en-us/HT202078[/URL] This article by Apple may also be of interest: [URL='https://support.apple.com/en-us/HT202944[/url]']https://support.apple.com/en-us/HT202944[/URL] So Far: I've followed all the basic and not so basic. I've cleared (I think) all the related plists. Maybe I'm missing one. I've cleared the keychain of messages (did I miss something?). NRAM/PRAM, safety mode (didn't work), and some other random stuff. Nothing. Please map out any tech support step by step so I can be sure i don't miss anything. Thank you!!!!