Crises is the only way to make the noun crisis plural. Confusion arises because some mistakenly believe that all nouns ending in s should form a plural that adds es to the end of the word.
Whenever you’re writing about a crisis, you have to decide whether you’re writing about one crisis or many. If you’re writing about a single crisis, then it should be in the singular form. If you’re writing about multiple crises, then it’s plura