Unselected tabs disappear - wpf

Question

I'm trying to fix a problem on a WPF app that was written, and seems to have worked, on Windows XP and Windows 7. On Windows 10, we're having a problem with unselected tabs disappearing.
The main window has a TabControl that has a custom style applied to its TabItems:
<TabItem
x:Name="dashboardTab"
Header="Dashboard"
Style="{StaticResource mainTabStyle}"
>
<local:DashboardControl x:Name="DashboardControl"/>
</TabItem>
The style:
<Style x:Key="mainTabStyle" TargetType="{x:Type TabItem}">
<Setter Property="Margin" Value="10,5,0,0" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TabItem}">
<Grid x:Name="ContentWrapper">
<ContentPresenter x:Name="ContentSite" VerticalAlignment="Bottom" HorizontalAlignment="Center" ContentSource="Header" Margin="12,2,12,2" Width="150" RecognizesAccessKey="True" />
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter TargetName="ContentWrapper" Property="Background" Value="AliceBlue" />
<Setter TargetName="ContentSite" Property="TextBlock.FontWeight" Value="Medium" />
<Setter TargetName="ContentSite" Property="TextBlock.Margin" Value="12,2,12,8" />
<Setter TargetName="ContentSite" Property="TextBlock.FontSize" Value="{Binding RelativeSource={RelativeSource AncestorType={x:Type Window}}, Path=FontSize, Converter={StaticResource mathConverter}, ConverterParameter=5}" />
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsSelected" Value="False" />
<Condition Property="IsMouseOver" Value="True" />
</MultiTrigger.Conditions>
<Setter TargetName="ContentWrapper" Property="TextBlock.Foreground" Value="Black" />
<Setter TargetName="ContentWrapper" Property="Background">
<Setter.Value>
<SolidColorBrush Color="White" Opacity="0.5" />
</Setter.Value>
</Setter>
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsSelected" Value="False" />
<Condition Property="IsMouseOver" Value="False" />
</MultiTrigger.Conditions>
<Setter TargetName="ContentSite" Property="TextBlock.Foreground" Value="White" />
<Setter TargetName="ContentWrapper" Property="Background">
<Setter.Value>
<SolidColorBrush Color="White" Opacity="0.15" />
</Setter.Value>
</Setter>
</MultiTrigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
The idea is to change the look of the tab item headers to look less like tabs and more like a row of selection buttons.
If I remove the style from the TabItems, I get a perfectly ordinary looking set of tab headers. If I leave it in place, under Windows 7 it works fine. The selected tab is highlighted with a light blue background. In Windows 10, though, the unselected tabs are invisible. The foreground text seems to be white.
Unfortunately, our WPF expertise has walked out the door, and I'm stuck trying to fix this. I know that its this style that controls the visibility. As I said, if I remove it I get normal tab headers. If I leave it in place and change the background color from "AliceBlue" to "Red", I see the change.
My question: how do I change this style to apply a specified foreground color to the textblocks of unselected tabs?

Answer 1

In the last multi-trigger, you are setting the TextBlock.Foreground property to White when IsSelected and IsMouseOver is false
This line right here <Setter TargetName="ContentSite" Property="TextBlock.Foreground" Value="White" />
And also you are setting the Background color to white in the following setter (i'm not sure what the opacity is for)
<Setter TargetName="ContentWrapper" Property="Background">
<Setter.Value>
<SolidColorBrush Color="White" Opacity="0.15" />
</Setter.Value>
</Setter>