Door Wont Lock?
 

So i bought a 2000 boxster s on sunday with 42000 miles, and cant figure out how the doors lock. when i hit the lock button on the key the doors go lock lock......pause......lock lock......beep beep and my doors and security system don't lock and security system doesn't go off it just lets me back into the car, so im not sure if there is something im missing, something wrong, or if its an easy fix...any help would be awesome.