Area will not light up in the sphinx

Hi Anyone,  I am not following a quest.  I decided on my first visit to Egypt to tackle the  Sphinx.  I got though to the back of the animal and through the maze O.K. and legitimately.  When my Sim climbed up the stairs he disappeared in to darkness.  My Sim was O.K. just that the area he had climbed to would not light up on his entry. I clicked on the control to go up a floor and I found myself outside looking at the lion's backside.  I was able to get him down again by clicking on the staircase and selecting 'Use Stairs'  I know that the deity in the final chamber will cure curses. My Sim is not currently cursed. Does my Sim have to be cursed?, or could I have missed something. 

Thanks in anticipation yours, BillFowerpot