Pool guy said that our water in our saltwater pool is “bad”

I’m new to pools so not quite sure what he means. We replaced the salt cell last year per his request but he says that the water is still bad… He is now saying that if we don’t drain the pool entirely and replace it with new water, that the salt cell will soon go bad again.

Is there a way to adjust the salt cell if it’s not producing enough chlorine or vice versa?

What should I be testing for?