ComboBox not opening when add code

Question

I am trying to add a ComboBox in the code to a WPF UserControl. The ComboBox is added as expected and shows the default I set in ComboBox, but when I press it, it does not open up.

This is the code with the Data that is trying to get bound, only part of it:

public class SelectRecentData : INotifyPropertyChanged
{
    public ObservableCollection<ComboBoxItem> projectItems { get; set; }
    private ComboBoxItem _selectedprojectItem;

    public ComboBoxItem SelectedprojectItem
    {
        get
        {
            return _selectedprojectItem;
        }
        set
        {
            this._selectedprojectItem = value;
            this.onPropertyChanged("SelectedprojectItem");
        }
    }
}

This is the code for generating and inserting the ComboBox:

SelectRecentData Data = new SelectRecentData();
ComboBox cbo = new ComboBox();
cbo.SetBinding(ComboBox.ItemsSourceProperty,new Binding(){
        bind.Source = Data; //Data is the class mentioned above
        bind.Path = new PropertyPath("projectItems");}
cbo.SetBinding(ComboBox.SelectedItemProperty,new Binding(){
        bind.Source = Data;
        bind.Path = new PropertyPath("SelectedprojectItem");});
cbo.Name = name;
cbo.Margin = new Thickness(0.5,0.5,0.5,0.5);
cbo.Width = 200;
sp.Children.Add(cbo); //sp is the StackPanel

This is the code for test adding items if you press a button on the page:

var defaultvalue = new ComboBoxItem { Content = "Added "+mycounter };
Data.projectItems.Add(defaultvalue);
Data.SelectedprojectItem = defaultvalue;
mycounter++;