photo stream update several days behind - what is the problem?

I am using the latest version of iPhoto 9 - 9.5.1. Has anyone had trouble with your photostream not stying up to date with your other devices? I have a few days worth of photos that are still not showing up in iPhoto ( mac ) and since there is no manual sync feature I am not sure what I need to do so these photos are synced to my mac - short of plugging in the phone but that defeats the purpose of having photostream turned on.