I was using the Craftsman two-stroke weed whacker and put it down to change
the cutting string and when I picked it up to pull the starter cord, it
would only move about five inches.

So I took out the torx screws holding the cover over the pull string, and
the whole unit came out easily.

But still the cord doesn't unwind.

I even removed the center torx bolt inside, but I don't know how that thing
comes apart - and - if it did - I might have a spring-loaded tension to
worry about.

Can you tell me, since I have no experience with this, what the problem
typically is?

What did I do wrong?
What can I do to get the string to wind again?

Note: The piston seems to move fine as I can twist the crankshaft without
any problem.