Does the owners manual have a good description of what to do here, also it
is possible something may have damaged a sensor during the tire repair if
each wheel has it's own pressure sensor and it does not work with the abs.

I'm not sure how powerful the magnet has to be....but you
could try buying one of those small horseshoe style magnets
and give the reset procedure a try.  Key on.....hold lock and
unlock buttons on your key fob at the same time until the horn
chirps....then hold the magnet at the left front wheel until the
horn chirps, move around the car clockwise, the left rear wheel
will be last, and the horn should chirp twice when that wheel
has been relearned.

If this doesn't work, you might have to take it in to the dealer....
again, I'm not sure how powerful the magnet has to be....the
service manual explains that the magnet simply activates an
internal magnetic reed switch which puts the sensor into
the "learn" mode.  You'd think that pretty much any kind
of magnet would work.

Ian