Please close SS and uninstall it by going to your Applications and right click the SS icon and select  "Send to Trash".  After that, download from the link below and reinstall. 

When you reinstall, PLEASE install it in the Applications folder for it to run correctly.   When you first click on the dmg file you download it will open a small window with the SS icon and a image of the Applications folder.  Simply drag the icon onto this Applications folder and let go.  This should install it correctly.

After that open Song Surgeon and then open a song and check to see if key detection is  now working. If not, please complete a Ticket here at the Help Desk.