Urg. Well I deleted the app and left the beta, hoping it would fix that, but apparently the multiplayer update hasn't rolled out on Android in Europe yet on the production version.
From twitter it sounds like there were still some hiccups with the servers and the Dev paused the rollout to sort it.
Probably why the game invite I sent didn't show up until much later, assuming it didn't only show up for you. (only sent one for The Field of Tribes)
Will update my code when I jump back into the beta again, so go ahead and drop the halfvoid in your friends list. (beta's full now, guess I get to wait)