I'm making a koth map, and I keep spawning below the map.
There isn't a spawn entity there, or anything. I spawn outside of the map's bounds in a black void where I stand, immobile, staring into the playing area. The map origin isn't at that position and I found no issues with my spawn points.
The only explination is that the spawn points are blocked, or set to the wrong team. Make sure your spawn points are floating a little above the ground, as you'll spawn on the first surface below the spawn