Living things reverse the increase in entropy but the entropy of the entire system is always increasing.

In this case, you can think of the "system" as the sun and the earth. The sun is a source of energy caused by fusion. That energy flows to Earth in the form of solar radiation (light, heat, etc.) On Earth, plants use that radiation to locally reverse entropy by using sunlight to power photosynthesis. Plants are the bottom rung of the food chain which leads to all other life on earth.

But that conversion is not 100% perfect; some energy is simply lost (it becomes heat re-radiated out into space where it slowly loses its energy).

So in the sun-earth system you have a state of low entropy (the sun) feeding a state of higher entropy (the earth after heat losses). Even though plants decreased entropy and other biological processes decreased entropy locally, the net entropy of the sun-earth system goes up.