Stop leak is extremely controversial. Some people insist that it always works unless you do something wrong. Did you carefully follow directions and it failed? Obviously you did something wrong! Some people insist that one product is the miracle cure and everything else is snake oil, but that probably supplies to every product. Shouty Kilmer has several videos promoting different stop leak products and I remember he poured one product into a cup and showed that it was clear and green, without anything to clog up coolant systems. For a while Subaru ordered all of their dealerships to use a stop-leak product, but I do not know how that worked out.
This is what Eric the Car Guy says about it: