I am posting here since this IS an AUTOPILOT issue I think or is it an Approach issue?  Although I am only a simulator commercial pilot, I was able to train on Boeing 757/767 CBT through the generosity of a close friend who is a captain for a large airline.  Anyway, when pushing APP, it is my understanding that all three CMDs are to activate for a LAND3 approach.  Mine don't.  What am I doing wrong.  I have lnav pushed and runway selected in the CDU no discontinuity.  Anyone who has the answer please help me out here.  I am tired of landing my plane manually when it cound autoland. Reading the CS manuals has not helped and Boeing says they should.  PS I was under 1500 feet and on glidepath but Approach was not descending. :-/