Still showing no cya

Hi I want to thank everyone for their great pool advice my new pool water has been crystal clear and clean since we opened it using the bleach borax method! However, I can't get the cya level up. I have a 19000 gallon 28 ft round pool and I added cya (about 3 lbs) but my level still reads zero. I did not add more because when I read another post, it said to cut the level recommended by 1/3 to 1/2 because you can only drain off the acid. I am doing the test according to the directions on the PS 234 kit, does anyone have any suggestions? Thanks

CYA takes a few days to show up in the test. When did you put it in?

According to the bleach (cya) calculator, 3 lbs. would only take you to 20 ppm. The cya test will not show really show any level below 20. Dave's question above is good - when did you add it?