M,
Silly, I know but I have to ask... I assume the pump was running, when the cell had no lights???
I also assume that the pump shuts off at night, and then when the pump comes back on in the morning the cell starts working again..
I had a similar problem where the cell would be working fine... the cell light would come on when producing chlorine and off when not producing chlorine, just like it should.. But, intermittently, when the cell light came back on, all the lights would go out and it would not come back on line unless I recycled power. It was intermittent, but would happen at least once a day, sometimes several times a day...
I shot a phone video of it and sent it to my pool builder, who sent a tech out to look at it. Of course the tech was only here for about an hour and it never went bad during that period. The pool builder called the local Pentair repair center and they just came out and replaced the cell... it was about three years old at the time and still under warranty..
Obviously, the problem went away when the cell was replaced.
I suspect you have the same issue...
Thanks for posting,
Jim R.