I can not sign in iMessage in my macbook

HI,

Is the Apple ID you are using in the iMessages account in Messages the same one you are using on an iPhone (or iPad).

Does it work on the iPhone ?

What error messages are you seeing ?

10:53 pm Monday; November 18, 2013

 iMac 2.5Ghz 5i 2011 (Mavericks 10.9)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
 Couple of iPhones and an iPad

It says check your network and try again but my internet is working fine?

Messages – Can’t log in

Messages - Error Processing Registration

Hi,

That is one of the "first 4" that Apple have addressed here, FaceTime, Game Center, Messages: Troubleshooting sign in issues - Apple Support

There are some other issues one of which has a large Error messages pane involving contacting Apple Support, and some that appear to have you logged in but no functions seem to work.

Try all the suggestions in the Apple Doc and post back with results.

9:21 pm Wednesday; November 19, 2014