If you have de blowing back into your pool, that most likely means your de grids need to be cleaned, or replaced. Open up the filter, clean the grids and check for tears and damage. If they are, replace them! If you can get them clean the new de may have a better chance of catching on them and being able to do their job.
If you have a de filter and your pool doesn’t get clean, stays cloudy, or you experience other water chemistry challenges, always check the grids. They should be rinsed down once or twice a season and thoroughly cleaned with a muriatic acid solution at least every other year, or as they indicate they need a more aggressive cleaning!