[SyntaxQ]

pawn Код:

public OnPlayerDisconnect(playerid,reason)
{
    new pname[MAX_PLAYER_NAME], string[128];
    GetPlayerName(playerid, pname, sizeof(pname));
    format(string, sizeof(string), ">> %s has joined the server (Reason: %s).", pname,reason);
    SendClientMessageToAll(0xF4A419AA, string);
    return 1;
}

lol, there you have mistyped it as joined, it should be disconnected or something..
Anyways, nice gamemode.