Making a timed room transition

[Chilton]

Ok
To go into more detail, im trying to make a script for a map in which you are transitioned into the map (Irrelevant), then after a set time, you automatically move to a new map.
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void OnStart()
{
AddTimer("Countdown", 500f, "CountdownHallucination");
}

void CountdownHallucination(string &in asTimer)
{
ChangeMap("map 3.map", "PlayerStartArea_1", "player_climb.snt", "player_crouch.snt");
}
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^^ Is what i currently have, and the script is accepted, but after the 500f, nothing happens. I even left it for longer and nothing happens.
What am i not doing here?

As usual, any guidance is much appreciated.