My iMessages are not successfully syncing. When I log in some old messages from a month ago starts coming in and then it stops. Once I close out of my computer, come back in after a few hours, more messages start to come in. What’s the problem?

My messages aren’t syncing with my MacBook Pro mid 2012 running OX Yosemite, version 10.10.4. Whenever I log in after a couple of hours a few start arriving and then it stops. Once I close my computer, log in, more will start to come in but they all have not synced. All my new messages arrive just fine but my old messages from 10/31/2005 have not synced but I realized that it is mainly from android users. Could this be a known problem and how would I fix this?