当我程序化地打开一个文档时，MS Word自定义任务窗格将消失

I am trying to create a simple MS Word addin (mostly to explore functionality). The addin adds a Custom Task Pane, and group in the Ribbon. The Ribbon controls include a checkbox to control the visibility of the Custom Task Pane, and a button to open a document. When I test the addin in MS Word the task pane shows up correctly, and the checkbox works correctly. The problem is, as soon as I click the button and open a new document, the task pane is hidden, and the checkbox no longer controls the the task pane's visibility. What is going wrong? How can I keep the custom task pane showing?I am trying to create a simple MS Word addin (m