When I start a mission in ALIVE, the current Force Pool is at 0, what does it really mean in ALIVE? Is that normal?

I had the same issue a few days ago. Turns out the players faction was not of the same faction as that used by the Military AI.

So if you are using CUP USMC, for example, for the Alive Military AI module, make sure 'player' is a cup faction.

Good luck!
DrDetroit