Sounds not playing from indicator alerts

Can anyone suggest why I can never get alerts to play sounds from indicators?  I am a recent CTrader convert so suspect its something basic ….

Example indicator below:

using cAlgo.API;
using cAlgo.API.Indicators;

namespace cAlgo.Indicators
{
    // Updated enum with a "Both" option
    public enum NotificationOption
    {
        Up,
        Down,
        Both,
        None
    }

    [Indicator(IsOverlay = true, TimeZone = TimeZones.UTC, AccessRights = AccessRights.FullAccess)]
    public class PriceCrossWMAAlert : Indicator
    {
        [Parameter("Period", DefaultValue = 21, MinValue = 1)]
        public int Period { get; set; }

        [Parameter("Source", DefaultValue = MovingAverageType.Weighted)]
        public MovingAverageType Source { get; set; }

        [Parameter("Alert Sound File", DefaultValue = @"C:\Users\steve\Sounds\Alert.wav")]
        public string AlertSoundFile { get; set; }

        [Parameter("Play Sound", DefaultValue = true)]
        public bool PlaySound { get; set; }

        [Parameter("Notification Option", DefaultValue = NotificationOption.Both)]
        public NotificationOption NotificationOption { get; set; }

        private WeightedMovingAverage wma;
        private DataSeries priceSeries;
        private int lastAlertedBar = -1;

        [Output("WMA", PlotType = PlotType.Line, Thickness = 2, LineColor = "#FFA500")]
        public IndicatorDataSeries WMAOutput { get; set; }

        protected override void Initialize()
        {
            wma = Indicators.WeightedMovingAverage(Bars.ClosePrices, Period);
            priceSeries = Bars.ClosePrices;
        }

        public override void Calculate(int index)
        {
            // Plot the WMA on the chart
            WMAOutput[index] = wma.Result[index];

            // Ensure we have enough bars for a valid WMA reading
            if (index < Period)
                return;

            double currentPrice = priceSeries[index];
            double previousPrice = priceSeries[index - 1];
            double currentWMA = wma.Result[index];
            double previousWMA = wma.Result[index - 1];

            // Only alert once per bar
            if (index > 0 && index != lastAlertedBar)
            {
                bool crossedUp = (previousPrice < previousWMA && currentPrice > currentWMA);
                bool crossedDown = (previousPrice > previousWMA && currentPrice < currentWMA);

                // If a cross is detected, decide if we should do anything
                if (crossedUp || crossedDown)
                {
                    // Cross UP logic
                    if (crossedUp && (NotificationOption == NotificationOption.Up || NotificationOption == NotificationOption.Both))
                    {
                        if (PlaySound)
                            Notifications.PlaySound(AlertSoundFile);

                        Print($"Price crossed UP WMA({Period}) at {Bars.OpenTimes[index]}");
                        // Optionally: Notifications.SendNotification(...);

                        // Draw UP arrow
                        double arrowPrice = Bars.LowPrices[index] - (Symbol.TickSize * 30);
                        Chart.DrawIcon(
                            "UpArrow" + index,
                            ChartIconType.UpArrow,
                            Bars.OpenTimes[index],
                            arrowPrice,
                            Color.Green);
                    }

                    // Cross DOWN logic
                    if (crossedDown && (NotificationOption == NotificationOption.Down || NotificationOption == NotificationOption.Both))
                    {
                        if (PlaySound)
                            Notifications.PlaySound(AlertSoundFile);

                        Print($"Price crossed DOWN WMA({Period}) at {Bars.OpenTimes[index]}");
                        // Optionally: Notifications.SendNotification(...);

                        // Draw DOWN arrow
                        double arrowPrice = Bars.HighPrices[index] + (Symbol.TickSize * 30);
                        Chart.DrawIcon(
                            "DownArrow" + index,
                            ChartIconType.DownArrow,
                            Bars.OpenTimes[index],
                            arrowPrice,
                            Color.Red);
                    }

                    // Mark this bar as alerted so we don't repeat on subsequent ticks
                    lastAlertedBar = index;
                }
            }
        }
    }
}