No Cyanuric Acid?

[PoolDoc]

Yes, it's possible you have none.

Some common types of soil bacteria can 'eat' it, and then 'poop' out either ammonia or nitrogen. I'm not sure how you're testing -- 'guess-strips' are never very accurate, and the stabilizer guess-strip test is the worst of them all.

An easy way to confirm no CYA is to
1. turn off your SWCG
2. add 5 ppm of chlorine via bleach (about 1.5 gallons of plain 6% household bleach) in the EVENING.
3. Test in the AM -- if chlorine is low, you have OTHER Problems.
4. Test that evening -- if it's a sunny or partly sunny day, and you have chlorine, you have stabilizer. If you have no stabilizer, you'll have no chlorine at the end of a sunny day.

[Strongmad]

I test the pool with a test kit, not the bonk strips.

I put in 1.5 ish gallons of bleach last night, plenty of Chlorine this morning. I'll test tonight to see if there is any left. It's gonna be plenty sunny today.

[PoolDoc]

I test the pool with a test kit, not the bonk strips.

If you used the 'cloudy water' test for CYA (melamine precipitation), and got a zero result . . . it's zero. The remaining question is, did the CYA go to nitrogen gas (no problem) or ammonia? If it's ammonia, you'll see high combined chlorine levels, and low free chlorine. You have to use a DPD test kit to get good info on that.