Empty Box

This is a photo of my purpose-built bluebird box shortly after I installed it on a post a few autumns ago.  It looks much the same today, albeit more weathered.  And that's because it is empty.  No bluebirds have taken up residence, nor any other birds for that matter.  I thought a pair of bluebirds were making a play for the box a few weeks ago but evidently the Missus had other thoughts.  And again, I come up empty.  This box has been a perennial disappointment.  It may be time to make a change.  Perhaps I need to rotate the box away from its current orientation?  Which way to face? east? west?