There's a possibility that your prop is affecting the light. Try hiding it or temporarily removing it and seeing if the light starts to work.
That's it. Somehow prop will block lighting to ground but not to other entities, I have no idea why because light_spot is definitely not inside prop's model. Now I have to sort out how I could use that model anyway
Actually my map is somehow broken: I copied lamp model plus light from the other map and it stopped working in my map. Weird