Its under development, its not out yet, you can only play standard and chess960 with the computers.
Crazyhouse vs Computer

I really want to play crazyhouse against the computer but no is said no! I’m going to be the first person to play crazyhouse against the computer but i am hoping i can talk to the manager of chess.com as soon as i can once is am 18. But i am sadly only8 almost 9 so i am afraid that i am not going to be able to do that for a long long long long long long long long time from now. But for now I will just have to play the boring old types against the computers for a very very very very very very long time from now.

I also think that they should put out a crazyhouse chess engine so we can play vs the computers mostly because it is very hard to get someone online to come play crazyhouse and haveing a cpu to play might just make it more fun to play as you don't have to wait 20 min for someone your level to play or play vs people who are way better or way worse than you.

I really want to play variants against the bots, because I am really bad at variants and I need some practise... I am very very very very very bad at variants (Especially crazyhouse) honestly.

I also think that they should put out a crazyhouse chess engine so we can play vs the computers mostly because it is very hard to get someone online to come play crazyhouse and haveing a cpu to play might just make it more fun to play as you don't have to wait 20 min for someone your level to play or play vs people who are way better or way worse than you.
Yeh I agree. It is really hard to find someone to play with. Would you like to play some variants or crazyhouse games with me some time? Note: I am bad at it. (Don't make it rated btw)

Crazyhouse is much more popular on lichess, they also have an engine for it/computer to play against
I went to play the computer, and saw the option for crazyhouse. I clicked on it, but when I went to start the game, it said, "You can't create a challenge, you are already playing the computer" (forgive the translation, it said it to me in French.). I assume what it meant to say was 'the computer don't play crazyhouse!"?