All the advice above is in line with my experience. Mine has frozen up
a couple of times over the years and the wrench did the job. With mine
I had to work the wrench back and forth a bit, then hit the reset
button. If there is a reset button and you don't use it, of course the
wrench by itself will not get it running again. Do try these things in
various order (really trial and error) as that is what it took for me.
I also got in there with my hand and carefull removed everything I
could find. One time some broken glass was the culprit.