Head directly to the main page (on us.playstation.com). Where it says 'sign in' to the right, go ahead and do so. You should now see your avatar synced up to your PlayStation Network ID, as through there you'll be logged into the PlayStation Network.
i have sort of the same problem, when i sign in playstation blog, it doesnt show my avatar for some reason now. but before in the past it did,not sure where i went wrong,if i did something or what.but would love for my avatar to show again.please let me know.thank you.