PvZ unable to connect multiple PCs

Through the router's control website (example 192.168.1.1) Try removing Port Forwarding rules (if exist) and remove any computers in DMZ.  Enable uPnP.

Test

If no, Disable uPnP and test.

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If no we can come up some more things to try.

Here  we used 2 computers on same network to play both modes together.

Thanks! I disabled the uPnP and then enabled it again - it worked after that.

The problem has reoccured - tried the same fix of disabling/enabling uPnP and it didn't work.  Are there any other fixes possible?  Surely Origin has patched these problems by now...

you cannot really fix this, because the game is an xbox import.

i can also not play Garden and Graveyards, for example, together with my son.

if you want to play with 2 comps from the same network online you have to set both comps to a FIXED IP.

Problem here, most static(fixed) modes are not supported by routers.

other possibility is that you run one comp over a proxy connection, but that player will have some little delay ingame then.

like 0.5 seconds from clicking to the actual shot.

http://answers.ea.com/t5/PvZ-Garden-Warfare-PC/2Pcs-2origins-2PvzGW-cant-play-together-y/m-p/3331949#U3331949

Maybe just try disabling uPnP and power cycling the router for a few minutes.

Check router for a firmware upgrade.  If the router supports Custom Firmware like DDWRT you might consider giving it a try.  Some of my friends have multiple Battlefields going in the same house and they use DDWRT.

We use a FreeBSD firewall as a router and it lets us play all our games together.  Some extra settings needed flipped around that most other routers don't have I doubt (like static ports).