View does not update UIElement property

I have a MainView with TabControl, which is intended to display child Views, and a ComboBox to display some values MainView has this XAML:

<TabControl ItemsSource="{Binding ViewModelsCollection, Mode=TwoWay}"
            SelectedItem="{Binding ViewModelsSelectedItem, Mode=TwoWay}">
    <TabControl.ItemTemplate>
        <DataTemplate>
            <TextBlock>
                <TextBlock Text="{Binding Path=Title}"/>
            </TextBlock>
        </DataTemplate>
    </TabControl.ItemTemplate>
</TabControl>

<ComboBox x:Name="cmbProfiles"
          ItemsSource="{Binding Path=ProfileCollection}"
          SelectedItem="{Binding Path=ProfileSelectedItem, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"
          DisplayMemberPath="Key">
</ComboBox>

Also, MainView has DataTemplates for child Views - to be used in the TabControl:

<Window.Resources>
    <DataTemplate DataType="{x:Type vm:OrdersViewModel}">
        <v:OrdersView/>
    </DataTemplate>
    <DataTemplate DataType="{x:Type vm:ShippingViewModel}">
        <v:ShippingView/>
    </DataTemplate>
</Window.Resources>

ChildViews are created in MainViewModel:

ObservableCollection<ViewModelBase> collection = new ObservableCollection<ViewModelBase>();

collection.Add(new OrdersViewModel());
collection.Add(new ShippingViewModel());

this.ViewModelsCollection = collection;

Each ChildView has a button, which IsEnabled property should depend on MainView's cmbProfiles selection:

<Button IsEnabled="{Binding Path=BtnServiceSetupIsEnabled}"
        Content="Next ...">
</Button>

Code in MainView to handle that:

IOrdersViewModel ordersViewModel = (IOrdersViewModel)this.ViewModelsCollection.Where(x => x.GetType().Equals(typeof(OrdersViewModel))).FirstOrDefault();

if (profileItem.Key == "Custom")
{
    ordersViewModel.BtnServiceSetupIsEnabled = true;
}
else
{
    ordersViewModel.BtnServiceSetupIsEnabled = false;
}

The problem occurs when I change selection in cmbProfiles: ChildViewModel.BtnServiceSetupIsEnabled gets updated in code indeed, but the ChildView doesn't reflect that change, button stays disabled. It does work fine if I don't use DataTemplates and simply add <v:OrdersView/> to my MainView, not dynamically filling the TabControl. How can I fix that - and to have my TabControl's TabItems created dynamically?