Why is my visibility binding not working?

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C#

XAML

Binding

Hello everyone,

I have a problem with one of my Visibility Bindings.
In my application I have a Textbox and a combobox at nearly the same place.
They are overlapping so I have two Variables in the background for their Visibility. They are in a Datagrid, so the Visibility Source will be provided from the list.

The Binding of my Combobox works absolutely fine, but the one of my Textbox doesn't

Here is my Code:

<TextBox x:Name="Textvalue"  HorizontalAlignment="Left" VerticalAlignment="Center" Width="150" BorderBrush="#FF383F55" BorderThickness="0" Foreground="White" removed="#FF232734"
                                                             Text="{Binding Path=Value, UpdateSourceTrigger=PropertyChanged}"
                                                             Visibility="{Binding Path=IsPath}"/>
                                                    <ComboBox x:Name="Combobox" VerticalAlignment="Center" Foreground="White" Margin="3,3,3,3" Height="23"
                                                              ItemsSource="{Binding Path=ValueArray}" 
                                                              SelectedValue="{Binding Path=Value, UpdateSourceTrigger=PropertyChanged}" 
                                                              Style="{DynamicResource ComboBoxStyle1}" 
                                                              Visibility="{Binding Path=IsCombobox}"/>

These are my Get Property for both (Both only have the Get Proberty):

public System.Windows.Visibility isPath
        {
            get
            {
                return _IsPath;
            }
        }

public System.Windows.Visibility IsCombobox
        {
            get
            {
                return _IsCombobox;
            }
        }

I hope you can help me because I don't know what's wrong here :/
Thanks in advance

What I have tried:

Tried to change the binding to a different Variable.