As Poliigon no longer supports the Specular workflow, how you set up materials in Keyshot may change going forward. Please reference Keyshot's Material documentation for in-depth information on all aspects of material creation in Keyshot :
When choosing a material type, you may need to select 'generic' or 'advanced' material type in order to expose the appropriate sockets to work with Poliigon's texture maps.
The following video can be used as a quick reference for basic material setup, however please note that specular files are no longer available on Poliigon.