HB, is the wheel mounted on the bike, or are you trying to spin the sprocket with the wheel off, as your photo shows? That sprocket will not turn. That's how it drives the wheel. If the wheel doesn't turn with it mounted in the bike frame, you've probably tightened the cone nuts too tight. They adjust how much bearing preload you have. Loosen the inner nuts just a little and see if the wheel spins when it is mounted in the bike. If it does then snug them up until you have no wobble in the bearings, no more, no less, then tighten the outer nuts that are on the outside of the frame while holding the inner nuts so they don't tighten along with them. You'll need a cone wrench to make this easier because they are made thin enough to fit between the frame and the hub. Get back to us with what you find.
Tom
Tom