They are not compatible with the crossbow. Those enchantments only work on the bow. Enchantments for the crossbow are: multishot, quick charge and piercing. I believe multishot and piercing are also mutually exclusive. You can also put unbreaking and mending on the crossbow too.
I decided to try out the crossbow by enchanting it with Infinity and Flame. But for some reason neither of these work. Why?
They are not compatible with the crossbow. Those enchantments only work on the bow. Enchantments for the crossbow are: multishot, quick charge and piercing. I believe multishot and piercing are also mutually exclusive. You can also put unbreaking and mending on the crossbow too.