<< Not an expert but I did have this happen this year.
Vac'ed it good, got chems where they should be and just couldn't rid of cloudy water. Like so white I could see it when back washing or in a measuring cup. PH was a little low, go that all back in shape and just wouldn't clear.
(This is at my old house and that I rent out, so I am not there 100% of time, which wasn't helping. )
I'm looking at pool frustrated Sunday and think what could be fighting this?
I went through the list in my head that I have read here numerous times, lights (no light fixtures), skimmers (clean), all places for algae.
I look across the pool at my steps. I kept thinking ladder, was not thinking steps. I have brushed all around it and over it, but ok let's try.
I unhook and pull it up, and when I let it part way back down to regrip it, and large green cloud flows out around it.
It was a green algae farm at the bottom of the steps. molded plastic and it has some tight, hidden areas.
Green sludge dripping out. So gross.
I was almost mad at myself for missing this but just so glad that I had most likely found it.
Scrubbed, washed, bleached and left it to dry in the sun.
Now we are SLAM-ing without that green farm and I expect BIG changes, likely by tonight.
I know better, always pull the stuff out but have been trying to do to many things and not concentrating.