Waterproofing treatments are available in a wide selection of brands and types. For old-school treatments, there are really two main varieties: oil-based and silicone-based. You needed to know which to use.
Leather that was oil-tanned needs an animal-oil-based product. Leather that was chrome-tanned needs a silicone-based product.
When the wrong treatment is used, it can’t penetrate the leather because the ingredients are noncompatible. Any waterproofing achieved will be very short-lived. It also voids some manufacturers’ waterproof warranties.
However, these days there are great products that work well on most leathers.
Your boot sales personnel should be able to help you when you make a purchase, or check with a good outdoors store. Your best bet, however, is to call the manufacturer. Most are very happy to help with that kind of information, as it is also in their best interest.