ASP.Net GridView Delete Button not firing

I've created an exact copy of this tutorial (vb)

http://www.aspsnippets.com/Articles/GridView---Add-Edit-Update-Delete-and-Paging-the-AJAX-way.aspx

However the delete click is not firing at all - I've removed the click confirmation too but the DeleteCustomers sub just isn't getting called. It compiles & runs fine with the edit/update actions.

Any ideas?