D,
Most cells last 5 to 7 years...
The "life left" is more just a guess and really means nothing in the big picture.
When in the normal mode, what does the Cell light do? If it is blinking and the cell is clean, then the cell is dead.
As a test, set the cell's output to 50% and watch the cell light.. It should on for about 2.5 minutes and then off for about 2.5 minutes.. This will just keep repeating.. If this works, then most likely the cell is making chlorine, but your pool is consuming it faster than your cell can make it.
What color is your water???
What is your CYA level??
What FC level do you normally try to maintain?
Thanks,
Jim R.