If you have the newest Adobe Reader which is called Acrobat Reader DC, your EPDM preview windows may have some extra panes that get in the way of previewing your file. Here is what it might look like:
The Bookmarks pane on the left and the Tools pane take up most of the space, leaving little room for the actual preview. You can eliminate the Tools pane by opening any PDF in Reader DC and then going to the View menu, selecting Show/Hide and then unchecking the Tools Pane item. This will hide the tools pane permanently for all documents. You will have to log off your machine and log back in (or restart the explorer.exe process from the task manager) for the change to appear in the EPDM preview window. I have not found a way to permanently remove the Bookmarks pane. If anyone has solved this problem, please let me know.