To Snipe34,
You do realize, because all the spawns are visible it would not work in multi with more than 2 players at least.
I did not know that! Really. How can I fix it?
Somehow you need to hide at least some zombieVolumes - so zombies will always spawn out of player view.  I had that problem with happyHour (with large numbers of players scattered all over the map -all in sight of zombieVolumes- no zombies came) which is why I made zombieVolumes at either end of the road and hid them with antiportals). Sorry, I'm not entirely sure about spawning behind antiportals but seems to work with HH...  I tried it with airport1 but that seemed to fail.
So hiding them in Octagon, tough one...  Easiest way probably, make a building above (unreachable by players) with a hole in the bottom so zs can drop down.  Then maybe elevators from platform to ground, for players/zombies.  I'm thinking strategy here, so zombies spawn from above forcing players groundward - occasional noob (or me lol) along one of the plats and has to jump.  Or you could make it tougher - buildings on the ground from which zombies spawn.  But the building above would be the fail-safe, which players can never see into, from there zs can always spawn.