Stephen Batchelor does an excellent job on summing up sunyata:

In this tradition, “emptiness” refers to the ultimate truth of all things. An exact analysis of the nature of phenomena leads us to the discovery that there is nothing whatsoever that can be said to constitute the “inherent existence” of anything. We instinctively believe that both ourselves and all other sentient beings and inanimate objects exist in their own right independently of everything else. When this supposed way of being—inherent existence—is exposed as an illusion, then we realize its emptiness. The realization of such emptiness is also called the “profound view.” It is realized not by denying anything “existent” but by negating something that has never existed at all. Insight into emptiness frees the mind from its most fundamental delusion and opens up a liberating experience of reality as it is. Even emptiness itself does not exist inherently. Emptiness is just as empty of self-existence as anything else.

We are “negating something that has never existed at all”, to arrive at “the ultimate truth of all things”.

The reason why there is not anything that has ever existed at all is because not anything has ever been created, or has arisen or been caused.

Whatever appears to have arisen are objects or events—phenomena—all of which are totally empty of actuality, or reality, or existence. To whom do they appear?: to persons who themselves are empty appearances, and thus equally lack reality.

All of the things which you presume exist or are real, are impermanent. “Ultimate truth” would not be impermanent. That which is empty could never have “arisen”. “Insight into emptiness” frees the dreamer from delusion.