Probiotics largely don't work - you can't colonize your gut by just taking a pill. The studies that show some effectiveness require you to take large amounts of antibiotics first to kill off all the bacteria in your gut. Then the most effective way to colonize is a fecal transfer.
https://www.newscientist.com/article/2178860-probiotics-are-mostly-useless-and-can-actually-hurt-you/