Equally, how do we know anything is not conscious?
How do I know that even I am conscious? Tautological or non-falsifiable "proofs" do not count. Serious question. I do not think that before this can be answered, there is absolutely no way to answer whether an AI is conscious.
How do we know we’re conscious ourselves?
Pretty sure that I am conscious. I am just not 100% sure that everyone else is.
Also: Peter Watts‘ novel Blindsight comes to mind here.