10 gallons of bleach on a typical 20x40 vinyl with deep end is about a 20 ppm dose of chlorine. (Gallons on straight rectangle vinyl pool are typically 30,000).
How are you testing? It needs to be with OTO -- the cheap test kits all use this, and it turn yellow to dark orange in the presence of chlorine.
Given the dosing you are doing, it's quite possible that your chlorine is so high it's bleaching out your chlorine test. OTO won't bleach out, so test with that.
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