what's wrong with my code?

MqlTradeRequest Request;
MqlTradeResult Result;
MqlTick Tick;

//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
void OnTick()
  {
   for(int i = 1; i<2; i++)
     {
      if(SymbolInfoTick(Symbol(),Tick))
        {
         Request.action = TRADE_ACTION_DEAL;
         Request.volume = 0.01;
         Request.order = ORDER_TYPE_BUY;
         Request.symbol = Symbol();
         Request.price = SymbolInfoDouble(Symbol(),SYMBOL_ASK);
         Request.type_filling = ORDER_FILLING_IOC;
         OrderSend(Request,Result);
         Sleep(1000);
         ZeroMemory(Request);
         ZeroMemory(Result);
        }

      if(SymbolInfoTick(Symbol(),Tick))
        {
         Request.action = TRADE_ACTION_SLTP;
         Request.position = PositionGetTicket(0);
         Request.symbol = PositionGetString(POSITION_SYMBOL);
         if(Request.type == ORDER_TYPE_BUY)
           {
            Request.sl = 21222.00;
            Request.tp = 26261.00;
           }
         else
            if(Request.type == ORDER_TYPE_BUY)
              {
               Request.sl = 26261.00;
               Request.tp = 21222.00;
              }
         OrderSend(Request,Result);
         ZeroMemory(Request);
         ZeroMemory(Result);
        }

      if(SymbolInfoTick(Symbol(),Tick))
        {
         Request.action = TRADE_ACTION_DEAL;
         Request.position = PositionGetTicket(0);
         Request.volume = PositionGetDouble(POSITION_VOLUME);
         Request.symbol = PositionGetString(POSITION_SYMBOL);
         ENUM_POSITION_TYPE Pos_type = (ENUM_POSITION_TYPE)PositionGetInteger(POSITION_TYPE);
         if(Pos_type == POSITION_TYPE_BUY)
           {
            Request.order = ORDER_TYPE_SELL;
            Request.price = Tick.bid;
           }
         else if(Pos_type == POSITION_TYPE_SELL)
           {
            Request.order = ORDER_TYPE_BUY;
            Request.price = Tick.ask;
           }
          OrderSend(Request,Result);
        }
     }
  }

Hi guys, I have some question

May I ask what's wrong with my code, it successfully place an order and modify position sltp,

but it can't close the position, why?