Working on Classroom in a Book Flash CS3 Professional (p 77 for those who have
it)

I drew a looped path for my rocket to follow, but
my rocket won't follow the path, it just flies from the beginning point to
the end point

I checked orient to path, sync and snap

Any ideas?

make sure the registration point of your instance are on the path, for both of the starting and ending keyframe.

Yes, it starts on the path and it ends on the path. It just doesn't follow it
in the middle.
Each student in the class is having the same problem, all working from the
Flash Classroom In a Book (CS3).

grab the instance in from the 'center' (the circle) point and it will snap to
the end of the path segment when you bring it close. in the case of a 'loop'
path as you'd described above, make sure that the line or 'loop' is not closed
entirely, stop it just short of the first point, that will tell Flash that it's
suppose to go around in one particular direction (ie. the long way). Once you
see the tween and can 'scrub' it, then you can adjust the endpoint, so that it
matches the 'distance' of movement in each frame, this will make the path
appear endless as the playhead jumps back to the first frame.