Mixing Matingale with RSI indicator

Hi, I am a beginer to C#, i am trying to make blend RSI bot from sample with Matingale and it has an Error:

Error CS0161: "MartinGaleRSI.OpenPosition()': Not a code path return a value (C:\User\ADMIN\Document\cAlgo\Sources\Robots\MartinGale + RSMartinGale + RSMartinGale + RSI.cs, line 84, column: 27)

how do i fix it? I would be very appriciate to everyone's help.

Here is my bot:

using System;
using System.Linq;
using cAlgo.API;
using cAlgo.API.Indicators;
using cAlgo.API.Internals;
using cAlgo.Indicators;

namespace cAlgo
{
    [Robot(TimeZone = TimeZones.UTC, AccessRights = AccessRights.None)]
    public class MartinGaleRSI : Robot
    {
        [Parameter("Initial Quantity (Lots)", Group = "Volume", DefaultValue = 1, MinValue = 0.001, Step = 0.01)]
        public double InitialQuantity { get; set; }

        [Parameter("Stop Loss", Group = "Protection", DefaultValue = 40)]
        public int StopLoss { get; set; }

        [Parameter("Take Profit", Group = "Protection", DefaultValue = 40)]
        public int TakeProfit { get; set; }
        
        [Parameter("Source", Group = "RSI")]
        public DataSeries Source { get; set; }

        [Parameter("Periods", Group = "RSI", DefaultValue = 14)]
        public int Periods { get; set; }
        
        private RelativeStrengthIndex rsi;

        protected override void OnStart()
        {
            rsi = Indicators.RelativeStrengthIndex(Source, Periods);
            Positions.Closed += OnPositionsClosed;
            ExecuteOrder(InitialQuantity, OpenPosition());
        }
       

        private void ExecuteOrder(double quantity, TradeType tradeType)
        {
            var volumeInUnits = Symbol.QuantityToVolumeInUnits(quantity);
            var result = ExecuteMarketOrder(tradeType, SymbolName, volumeInUnits, "SampleRSI", StopLoss, TakeProfit);

            if (result.Error == ErrorCode.NoMoney)
                Stop();
        }



        private void OnPositionsClosed(PositionClosedEventArgs args)
        {
            Print("Closed");
            var position = args.Position;

            if (position.Label != "SampleRSI" || position.SymbolName != SymbolName)
                return;

            if (position.GrossProfit >= 0)
            {
                ExecuteOrder(InitialQuantity, OpenPosition());
            }
            else
            {
                ExecuteOrder(position.Quantity * 2, position.TradeType);
            }
        }

        private TradeType OpenPosition()
        {
            if (rsi.Result.LastValue < 25)
            {   
                OnpositionOpen(TradeType.Sell);
            }
            else if (rsi.Result.LastValue > 75)
            {
                OnpositionOpen(TradeType.Buy);
            }
        }

        private void OnpositionOpen(TradeType tradeType)
        {
            var volumeInUnits = Symbol.QuantityToVolumeInUnits(InitialQuantity);
            var Valueposition = Positions.Find("SampleRSI", SymbolName, tradeType);

            if (Valueposition == null)
                ExecuteMarketOrder(tradeType, SymbolName, volumeInUnits, "SampleRSI", StopLoss, TakeProfit);
          
        }
    }
}