Thank you for assistance.. I did replace about 20% of water on Saturday.. and let pump run overnight . Levels on Sunday are listed below (readings from pool store using fancy equipment , but consistent with my own measurements using taylor kit).. I am putting in ~80 oz of dichlor into 37500 gallon pool (about 2 oz/1000 gallon) and chlorine still totally dissipated after a day. At the direction of pool store this time I deployed chlorine directly to the deep end ( i had been feeding through skimmer) ... One other piece of info is I am using Nature 2 cartridge.. is it possible Nature 2 did not activate? Thank you in advance for assistance!!

FC 0
TC 0.02
CC 0.02
pH 7.7
Hardness 167
Alkalinity 123
CYA 96
Copper 0.1
Iron 0.1
Phosphate 320 ppb