Indicator and ChartObjects.DrawHorizontalLine

Hi

I have made the following indicator.

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

namespace cAlgo
{
    [Indicator(IsOverlay = true, TimeZone = TimeZones.UTC, AccessRights = AccessRights.None)]
    public class Test : Indicator
    {
        protected override void Initialize()
        {
            // Initialize and create nested indicators
        }

        public override void Calculate(int index)
        {
            // Calculate value at specified index
            // Result[index] = ...
        }

        public void DrawOpen()
        {
            ChartObjects.DrawHorizontalLine("Open", MarketSeries.Open.Last(1), Colors.Red);
        }
    }
}

And in the cbot i wrote the following lines in OnStart

Test testInd = Indicators.GetIndicator<Test>();
testInd.DrawOpen();

But the line is not being drawn.

But if the function is in cbot, the line is drawn.

What am I doing wrong?

Thanks