Listbox items not wrapping, tried almost everything. it might be due to ItemTemplate

**Tried adding wrap panel as parent, as child, as item template parent, but didn't work
**

    <UserControl.Resources>
<DataTemplate x:Key="CredentialTemplate" DataType="{x:Type local:Credentials}">
<WrapPanel Width="800" Orientation="Horizontal">
<Grid Background="Red" Width="160" Height="160">
<Grid.RowDefinitions>
<RowDefinition Height="40"/>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<TextBlock Grid.Row="0" Grid.Column="0" Text="{Binding FileName}" FontWeight="Bold" Margin="0,0,10,0"/>
<Button Grid.Row="1" Grid.Column="0" x:Name="btnCopyUsername" Tag="{Binding Button}" Content="Copy Username" Click="OnCopyUsernameButtonClicked" Margin="10"/>
<Button Grid.Row="1" Grid.Column="1"  x:Name="btnCopyPassword" Tag="{Binding Button}" Content="Copy Password" Click="OnCopyPasswordButtonClicked" Margin="10"/>
<Button Grid.Row="2" Grid.Column="0" x:Name="btnEdit" Tag="{Binding Button}" Content="Edit" Click="OnEditButtonClicked" Margin="10"/>
<Button Grid.Row="2" Grid.Column="1" x:Name="btnCopyBoth" Tag="{Binding Button}" Content="Copy Both" Click="OnCopyBothButtonClicked" Margin="10"/>
</Grid>
</WrapPanel>
</DataTemplate>
</UserControl.Resources>
<WrapPanel Width="900" Background="Yellow">
<ListBox ItemsSource="{Binding Credentials}" ItemTemplate="{StaticResource CredentialTemplate}" ScrollViewer.HorizontalScrollBarVisibility="Disabled"  ScrollViewer.VerticalScrollBarVisibility="Disabled">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel Orientation="Horizontal" Background="Green" Margin="10"/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
</WrapPanel>
</UserControl>

It might be the grid control that not letting wrap, normally without item template it should work

Screenshot

I explored this issue with a simplified version of your markup.
I don't have a credentials class, but what's in the grids doesn't matter.

My markup has less wrappanels:

    <Grid>
<Grid.Resources>
<DataTemplate x:Key="CredentialTemplate">
<Grid Background="Red" Width="40" Height="40">
</Grid>
</DataTemplate>
</Grid.Resources>
<ListBox ItemsSource="{Binding Points}" 
ItemTemplate="{StaticResource CredentialTemplate}" 
ScrollViewer.HorizontalScrollBarVisibility="Disabled" 
ScrollViewer.VerticalScrollBarVisibility="Disabled">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel Orientation="Horizontal" 
Background="Green" Margin="10"/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
</Grid>

I've got 30 Points in my viewmodel.
My grid is smaller

Wraps ok:

List view Item Template with wrapping list view items
in my case i have sales man list and i am displaying sales man name in round button using Wrap Panel.

<ListView Grid.Column="1"  Grid.Row="3"  Name="lv" 
Style="{DynamicResource NewCollectionInfoModuleSalesRepListViewStyle}"
SelectedValue="{Binding Path=SelectedSalseRepData,
Mode=TwoWay, 
UpdateSourceTrigger=PropertyChanged,
NotifyOnValidationError=True, 
ValidatesOnDataErrors=True, ValidatesOnExceptions=True}"
ItemContainerStyle="{DynamicResource NewCollectionInfoModuleSalesRepListViewItemStyle}"
ItemsSource="{Binding Path=lstSalesRepresentative}">
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel />
</ItemsPanelTemplate>
</ListView.ItemsPanel>
<ListView.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.RowDefinitions >
<RowDefinition Height="80" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="188" />
</Grid.ColumnDefinitions>
<Button  Grid.Row="0" Grid.Column="0"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
Style="{DynamicResource NewCollectionInfoModuleSalesRepListButtonStyle}"
Background="{Binding Path=SelectedSalesRepColor,Mode=TwoWay}"
IsEnabled="False">
<StackPanel>
<TextBlock  Grid.Row="0" Grid.Column="0"
Style="{DynamicResource NewCollectionInfoModuleSalesRepListTextBlockStyle}"
Text="{Binding Path=Name,Mode=TwoWay}"
Foreground="{Binding Path=SelectedSalesRepTextBlockColor,Mode=TwoWay}">
</TextBlock>
</StackPanel>
</Button>
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>