How to enable DevExpress Grid Conditional Formatting?

I have a .net, C# Windows Form project. I'm using DevExpress 19.1. On my GridControl, I have conditional formatting for when a column is less than 0. I want the cell to be highlighted red when the value is less than 0, but it's not working. I've tried using an expression, a condition and value, applying to just a column, applying to the whole role, but I never get the highlighting to work. Can someone tell me what I'm doing wrong?

Here is how the rule looks liked in code:

        gridFormatRule3.ApplyToRow = true;
        gridFormatRule3.Column = this.colQuantityLeft;
        gridFormatRule3.ColumnApplyTo = this.colQuantityLeft;
        gridFormatRule3.Name = "Format0";
        formatConditionRuleValue3.Appearance.BackColor = System.Drawing.Color.FromArgb(((int)(((byte)(255)))), ((int)(((byte)(128)))), ((int)(((byte)(128)))));
        formatConditionRuleValue3.Appearance.Options.UseBackColor = true;
        formatConditionRuleValue3.Condition = DevExpress.XtraEditors.FormatCondition.Less;
        formatConditionRuleValue3.Expression = "[QuantityLeft] < 0";
        formatConditionRuleValue3.Value1 = 0;
        gridFormatRule3.Rule = formatConditionRuleValue3;
        this.gvProducts.FormatRules.Add(gridFormatRule3);

Here's how I set the rules in the Designer:

Here's the output where you can see the value is less than 0 and the background color is not changed:

I see that you have only one row in the grid. The grid always has a focused row. The focused row appearance has a higher priority than conditional appearance. Disable the GridView.OptionsSelection.EnableAppearanceFocusedCell and GridView.OptionsSelection.EnableAppearanceFocusedRow properties to remove the focused row appearance.

this.gvProducts.OptionsSelection.EnableAppearanceFocusedCell = false;
this.gvProducts.OptionsSelection.EnableAppearanceFocusedRow = false;

Alternatively, set the FormatConditionRuleValue.Appearance.Options.HighPriority property to true.

formatConditionRuleValue3.Appearance.Options.HighPriority = true;