- You need 1 info_player_intermission. I think that's the reason for the error displayed. The info_alien_intermission and info_human_intermission are not necessary to have a working map, but they are wanted of course.
- You need an alien and a human spawn (1 egg, 1 node). You need to place them above the ground, and it doesn't hurt to place them quite a few units (like 16 or more) above the ground to make sure that they appear and aren't swallowed by the ground. They also need enough headspace.
- You need a closed room, meaning: There must at least be one not leaking room in which there are spawns. Maybe you had a "LEAKED" text somewhere in your compile output.
EDIT: If you think you did all this, maybe you should open the map file with a text editor and re-check if everything is existing. Because user-errors with the editor happen to everyone.