Okay, so I am working on a coop minigame-type map. When I compile it, it is fine. When I type
"ss_map mp_coop_battle" (without quotes of course" The loading screen comes up, but when it gets to the third slide/image, about halfway through the game closes, nothing coming up, no error messages, no nothing. So, what am I doing wrong?

Have you set sv_cheats 1 followed by sv_lan 1 in the main menu? That works for me.

That just makes it stop responding and crash on the first slide/image.

Have you tried validating portal 2?

I verified it, and it went back to crashing on the third image.

Hmmm... Try loading a valve map. If that doesn't work, Im clueless. If it DOES work, try maknig sure everything is correctly set up in hammer. To test, I like to use the coop entrance instance. If it still doesn't work, try loading the coop lobby first, then load the map from there. If it STILL doesn't work, try making a random map that uses the coop entrance instance. Compile and load it. If that works, try loading your other map. If it doesn't, God help you.

Turn off tools mode. That did it for me.

There must be something wrong with the map . I compiled a custom map with the coop spawn instance, it worked, valve map worked, I went back to the map I made, it didn't work. I tried putting the coop spawn instance in, and it didn't work (I had different spawns for each player). I believe I've had tools mode off.

Do you have an Info_player_start? You always need that.

I did until I put in the coop spawn instance. So yes.