WPF Ivalueconverter Not firing

Here is my xaml below. The DisplayUnitConverter is not firing when I click the radio buttons.Can someone assist me to see what I am doing wrong?

xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

xmlns:dxe="http://schemas.devexpress.com/winfx/2008/xaml/editors"

xmlns:dxn="http://schemas.devexpress.com/winfx/2008/xaml/navbar"

xmlns:dxlc="http://schemas.devexpress.com/winfx/2008/xaml/layoutcontrol"

xmlns:DisplayUnitClient ="clr-namespace:DisplayUnitClient"

mc:Ignorable="d"

Title="MainWindow" Height="350" Width="525">