[Eoussama]

Try this:

PHP код:

CMD:respawnarmy(playerid)
{
    if(PlayerInfo[playerid][pAdmin] < 1) return SendClientMessageEx(playerid, COLOR_WHITE, "Dibutuhkan admin LVL 1+");
    for(new x;x<sizeof(ARMYVehicles);x++)
    {
        if(!IsVehicleOccupied(ARMYVehicles[x])
             SetVehicleToRespawn(ARMYVehicles[x]);
    }
    SendClientMessageToAll(COLOR_REALRED,"[Information] {FFFFFF}Kendaraan faction ARMY telah Direspawn.");
    return 1;
} 


You were passing the iterator to the parameter of the IsVehicleOccupied function, whereas you needed to pass the vehicle ID stored in the ARMYVehicles array, simply change !IsVehicleOccupied(x) to !IsVehicleOccupied(ARMYVehicles[x]).