Histogram-in-WL8-appears-as-line

My histograms are appearing as lines. Do I need to do something different?

CODE:
using WealthLab.Backtest;
using System;
using WealthLab.Core;
using WealthLab.Indicators;
using System.Collections.Generic;

namespace WealthScript5 
{
    public class MyStrategy : UserStrategyBase
    {
        //create indicators and other objects here, this is executed prior to the main trading loop
        public override void Initialize(BarHistory bars)
        {
         PlotIndicator(new PBSlowOsc(bars,14,5,3), WLColor.FromArgb(255,255,0,0), PlotStyle.Histogram);
        }

        //execute the strategy rules here, this is executed once for each bar in the backtest history
        public override void Execute(BarHistory bars, int idx)
        {
            if (!HasOpenPosition(bars, PositionType.Long))
            {
                //code your buy conditions here
            }
            else
            {
                //code your sell conditions here
            }
        }

        //declare private variables below

    }
}