I'm not positive, but this appears to be broken. I'm not sure if something supposed to be happening, but nothing seems to be going on.
Found the issue, thanks for pointing it out! Press P when you are ready for the first wave. There's a problem with the grace period never ending.
I say that and then they start spawning. It should take about 4-5 minutes to start spawning. Maybe try waiting a little longer if you can't use the P wave spawn key.
Thanks for the update!
