We did not have information on 3 natural nominations.
We can start the deduction with the assumption that those 3 are from different countries than those that have already nominated a cultural site for 2021 (as only 1 nomination is allowed).
From the ones I had on the 2021 page, these could be:
Hin Nam (Laos) (extension to Phong Nha Ke Bang)
Mountain Ecosystems of Koytendag (Turkmenistan) (deferred a few years ago but still active)
Mt. Mantalingahan Protected Landscape (Philippines)