WPF MVVM Binding to static entity not updating - wpf

Question

I have a base abstract viewmodel containing 2 static models. In a usercontrol, I bind to both. Only the one binding (language) resolves and updates when the underlying static model changes. The binding to Employee does not update the fields. I have tested that the Employee setter is called and indeed it is. The getter however does not get called after the value changes. Any guidance will be appreciated.
Base Viewmodel:
namespace POC.Windows
{
public abstract class ViewModel : ObservableObject, IDataErrorInfo
{
private static int _languageId;
private static Languages _language;
private static Employee _employee;
public Employee Employee
{
get { return _employee; }
set
{
_employee = value;
NotifyPropertyChanged();
}
}
public int LanguageId
{
get{return _languageId;}
set{
if (_languageId != value)
{
_languageId = value;
LoadLanguage(); //Async populate Language model
NotifyPropertyChanged();
}
}
}
public Languages Language
{
get
{
if (_language == null)
{
_language = new Languages();
_languageId = -1;
LoadLanguage();
}
return _language;
}
set
{
_language = value;
NotifyPropertyChanged();
}
}
//Async Loading functions here - omitted
}
}
UserControl View:
<UserControl x:Class="POC.DesktopClient.UserControls.EmployeeDetails"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:viewModels="clr-namespace:POC.DesktopClient.ViewModels"
mc:Ignorable="d"
d:DataContext="{d:DesignInstance viewModels:EmployeeDetailsViewModel}">
<UserControl.Resources>
<viewModels:EmployeeDetailsViewModel x:Key="EmployeeDetailsViewModel"/>
</UserControl.Resources>
<Grid>
<StackPanel Orientation="Vertical" Grid.Row="0" Grid.Column="0">
<TextBlock VerticalAlignment="Top" Margin="10"
Text="{Binding Path=Language.FirstName}"
Foreground="DarkBlue" FontWeight="Bold" FontSize="20">
</TextBlock>
</StackPanel>
<StackPanel Orientation="Vertical" Grid.Row="0" Grid.Column="1">
<TextBlock VerticalAlignment="Top" Margin="10"
Text="{Binding Path=Employee.FirstName}"
Foreground="DarkBlue" FontWeight="Bold" FontSize="20">
</TextBlock>
</StackPanel>
</Grid>
haven't touched the usercontrol's xaml.cs and EmployeeDetailsViewModel is empty:
public class EmployeeDetailsViewModel : ViewModel
{
}
---EDIT---
Observable Object:
namespace POC.Windows
{
public class ObservableObject : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void NotifyPropertyChanged([CallerMemberName] string propertyName = "")
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Additional information:
The Usercontrol is hosted in the MainWindow.xaml.
In MainWindow.xaml.cs a datacontext is defined as a MainViewModel (that also is blank and inherits from ViewModel).
The static Employee model is bound to a listbox's selectedItem property.
The listbox is in a separate usercontrol also on the MainWindow.
Ths listbox's viewmodel is also blank and inherits from the base viewmodel. Its xaml.cs is blank, datacontext is set in Xaml, same as the details usercontrol.
LanguageID is bound to a combobox selectedValue on the MainWindow.
So in a nutshell, when I change the language in the combobox, the usercontrol's labels bound to language updates correctly. When I select an employee in the listbox, usercontrol's labels bound to Employee remains blank.