Exact same issue here, I got it for my 10 year old for Christmas, and 5 days later, we can still not access it.
I get as far as the menu screen on the game, if I try multiplayer I get the error "You have been disconnected from the EA server, blah blah blah fish paste"
I spend a whole day going through these useless forums trying everything everyone else tried. Some suggests that you cannot connect because the host is disconnected since its a peer to peer game,and you are connecting to another player/players. Others suggest it has to do with openig certain ports on you router. Its been an absolute nightmare, not to mention my poor little boy who had been so eager to play this game on his new PS4 is now stuck looking at some stupid message that pops up.
It happens on every menu I click on, whether I try going into split-screen, options, every single menu returns this, so to me it has nothing to do with an unavaiable host, but rather a poor setup on the EA server.
This does not happen to any of the other games the kids play online, ONLY with Garden Warfare PvZ, what an utter waste of money.
I will most certainly think twice before buyig an EA game again.