Hi,
many people have this problem with cells over 3 years old- salt reading is 300-1000 ppm less than what was being tested in pool store(getting worse by time). Reading from pool store are correct.
When salt reading drop bellow 2300 ppm is Aqua Rite will shoot down output to cell( generating LED off). Chlorine generation will stop even actual salt level in pool is 2500-3400 ppm. But cell is still OK and can generate chlorine.
Problem is caused by salinity sensor that is part of cell, so we need to clean,calibrate it or replaced. Unfortunately, no one have details how to calibrate or replace this sensor, so you have to replace entire expensive cell .
Dusan