Looking for a realistic cracked leather texture

BIS is not related to Poliigon ) And it not depends on your operation system.
In what window do you try to get materials from the BIS add-on? You mast do it in the “Shader editor” (materials window) window! (If you try to do this in the “3D View” (window with meshes) window - this part of the BIS add-on is intended to get meshes, not materials.)