I don’t think kefir is for everyone, just like not everyone has the enzyme to process milk proteins in their genes. I would question what your food ate? Were you eating grain fed ruminant meat? Did you cut out everything but meat and clean water to start? It does take some time to recolonize your colon, your liver has to switch to metabolizing fat, and your bile production takes a bit too.

What liver tests did you have done?