I believe there are two reasons why we have failed to solve the hard part of the problem [of consciousness]. The first is philosophical and the second is scientific.
Physiological processes do not produce consciousness in the sense that the liver produces bile. Consciousness is not a thing but rather a point of view. What we perceive objectively as physiological processes in the brain we perceive subjectively as conscious states. These are two different observational perspectives upon the very same processes: consciousness arises from the being of a brain. This leads to a fundamentally different question: Why is it something to be a brain but not to be a liver, or, for that matter, a rock?
Not all bodily processes possess something-it-is-like-ness, and nor do all brain processes. This takes us to the scientific reason why we have failed to solve the problem: we have been focusing on the wrong brain function as our model example, namely visual perception. Visual perceptual processes are not intrinsically conscious.
Once we have come to these conclusions, the hard problem of consciousness assumes a new form, namely: “How and why do feelings arise?”