Cloudy water can be caused for a number of reasons: poor filtration, imbalance of chemicals in your pool such as total alkalinity, pH, calcium hardness and chlorine, imbalance of total chlorine and free chlorine (referred to as chlorine demand), etc.
It could also be that you have a lot of micro particles that your filter can’t catch. You might want to try a clarifier that makes the tiny particles clump together and easy to remove with a vacuum.
This condition occurred with me twice last year. The diagnosis for me was “mold”. I was using Bacquacil, and the dealer told me to test for mold by pouring 1 gallon of Bacquashock directly into the skimmer. If the return subsequently starts blowing white instead of clear water, it’s mold. The only recourse was to super chlorinate, which of course made a big mess, then vacuum and restart with Bacquacil again after the pool cleared up.
The water is cloudy due to poor water chemistry. Most likely it is a ph problem. Take the water into a pool store. Sometimes cloudiness is also due to using a calcium-based shock such as the brand Sock-It.
Double shock your pool with liquid chlorine (12.5%). A double shock is 2L of chlorine for every 10,000L of water in your pool. The cloudiness is likely the start of algae. You may also find a clarifier helpful after double shocking to help eliminate the particles that will settle to the bottom of the pool.
Make sure all of your levels are balanced. Then, if there is no improvement, add a clarifier ONLY if you are using a sand or cartridge filter, or it will clog the filter.
First make sure ALL your levels are good. Depending on the filter type that is used, perform a backwash vacuum. If using a sand filter, try some DE in small doses or it will clog the filter. Let it run through the filters. Watch your pressures and when they get to the point when you would normally backwash, then do so. Have a complete water analysis to find the cause for cloudy water.