The problem is how matter can have self-awareness. It's hard to describe in words, because all of the words to describe this (consciousness, feeling, awareness) have also been (ab)used to describe the non-mysterious processes that enable an organism to act in the same way as one that we believe has consciousness, feeling, awareness.

You can say you're a functionalist, and you believe that a system that accurately reproduces all the same observable behavior of consciousness necessarily will also reproduce consciousness. Supposing that were so; it wouldn't explain consciousness.

I think functionalism is the claim that consciousness is not epiphenomenal. Suppose functionalism is false, and something that behaves like a conscious system is not necessarily conscious. This would mean that a conscious system possessed some extra quality, "consciousness" which was not a behavior and is not observable. Hence, epiphenomenal.

Alternately, people could mean by functionalism that anything that reproduces all the behavior of a conscious system that we are currently capable of observing (or at least theorizing about, having the necessary concepts in our physics), is necessarily conscious. But that would be silly; it would be equivalent to the assertion that today's physics is complete.