Mo,
A flashing cell light on an IC40 means the cell needs to be inspected and most likely cleaned.. Not sure if you have done this already or not.
There should be no calcium build up on the internal plates. If there is, you need to soak the plates in diluted Muriatic acid.. 1 part water and 1 part MA.
They sell a cap that goes over the end of the cell that allows you to fill the cell with the MA solution.
It is best to use a garden hose and to remove as much scale as possible before using the MA.
I only soak long enough for the bubbling to stop and then I rinse the cell out...
Thanks,
Jim R.