I replace my Hayward aquarite salt cell with a generic simple cell at the end of last year. All worked fine for the final month of swimming. Trying to get things back up running now and am having trouble with salt cell generating chlorine. Had low flow light and low salt light on so cleaned filters as well as cell and low Flow light went off but low salt stayed on. Tested salt with Taylor kit and Brough salt level up to 3000 ppm. Salt level on screen is showing 1600. When I push switch from auto - off - back to auto and press button 5 times I see -2100 and it goes down from there so am unable to recalibrate to correct level. If I do the same thing a second time it shows - 400. If done a third time I see -2100 again. This back and forth between 2100 and 400 happens every time I try to calibrate. What would most likely problem be? Cell already failed?