Pentair IC 40 not making chlorine.

The unit is about 15 months old and is not making chlorine even though all the LED buttons that should be green are green with the exception of the very top LED button which is blinking indicating high salt. I have never had a salt reading higher than 3600and right now it is at 3450. Pool water has been checked by the best pool supply store in town, old pros who know what they are doing. Conditioner, PH, etc all are perfect. Water was checked for phosphates too...reading was zero. Large main filter is clean, SWG unit has been acid cleaned. I have been keeping chlorine in the water by adding a gallon of chlorine liquid every other day. Pool is about 40,000 gallons. Variable speed pump is running 10 hours a day. In the past when the unit was working properly I would set the unit at 60% and had plenty of chlorine. Now it is at 100% and does not seem to be producing anything. Have I missed something here....hard to believe the unit would fail in this short period of time.