Just to give some background.  I had my first LitterMaid for 6 years
until this past December when the spring mechanisim that recoils the
wire connected to the rake failed and the wire got wrapped around the
rake and eventually snapped.  Since my first LitterMaid had lasted so
long I didn't hesitate to run out and pick up a new one regardless of
the reviews (neg & pos) that I had read on the web.  I got the LM570,
it lasted a month and I brought it back to the store where purchased
and exchanged for another.  The motor had failed, it wouldn't engage
but the power light was on.

Now, 2 weeks later, I thought this replacement one had died with the
same symptoms.  Not impressed with LM Customer Service, I decided I
would bring it back to the store again for replacement.  As I was about
to pack it up, I noticed additional sensors that are not listed in the
manual.  In addition to the sensors located just above the litterpan
there are 2 metal sensors that the rake must hit when it gets to the
end of the track to reverse direction after dumping in the waste
receptacle.  They are just little strips of metal that detect the
pressure from the rake.  Well, there was a little hunk of litter stuck
in the sensor smaller than a pea.  I dislodged this and now my
LitterMaid is working again.

Hopefully this helps someone else!  Good Luck.