You don't say what make it is, try going to the makers first for a test kit, old test kits go out of date.
Try some simple tests first, is it using salt, is the by-pass valve closed and depending on make is there water in the brine tank and lastly has the salt formed a platform in the bottom of the brine tank. If it has clean all the old salt out and replace with new.
RM
August 2011