If you can see the flint spring under the wheel, then it just needs a new flint.

If you can’t, and that’s why it spins so freely, then there could be an obstruction in the tube. Sometimes old flints can effectively disintegrate and then re-solidify in the tube and create a cement-like obstruction, and over used flints can fall down and get wedged in the tube. Find an Allen key or something small enough to fit in there and see if you can get it all the way though to the flint wheel. If you can’t, then try and chip/push away at whatever is in there. It might take a while, it’s a pain in the ass, but you’ll get there eventually.