Jandy Aquapure R0452400 SWG

Bought house in Dec with 16,000 in ground Alt water pool…two weeks ago water test shows no free chlorine at all.  Added bleach, etc but after that chlorine dropped again to 0’ had an 125 and 194, so used acid and cleaned…I thought.

still getting check aquapure general fault message with a 79 code now?

Salt still shows 3000’ pH typically between 7.6 and 8, cy 45, hardness 230.  Have had low TA typically but add few pounds as needed.

how do I trouble shoot the swg?  Also need to mention I do need to replace the filter cartridges in general, 5 years old and reading dirty on my cv340.