Hi,
Tested and it works ok, check few things to debug this:
-- you need to specify the right Pool Name in the DeSpawn action
-- you need to to specify the right gameObject in the the DeSpawn action
That's pretty obvious, and you could have a problem earlier on, for example, are you sure you are storing the spawned gameObject in a variable when you spawn it? the spawn action let you do that.
I have attached a modified version of the test scene that comes with the set of actions, it despawn the cube after 4 secs ( check the "pool creator" fsm)
bye,
Jean