i saw the wip and i knew where this was going but didnt say something idk why
not enough contrast, not near enough
even though in the ref it might be subtle, you must make it obvious in the painting, you need to know that those value changes exist and show them off, otherwise it looks flat. Be bold in your value changes, dont be afraid to get real dark and real light on the planes of his face, if all the darks and lights are consolodated to his mustache, thats all that anyone will ever care about