Again flex, again errors, who can give cuff?

Question

css

How many times have I already run into a problem with these justify-content: center;
align-content: center; , therefore I demand a cuff and indicate where the error is.
This is a form (for educational purposes), it is not in a div or some other block, but simply in the body, but it is not centered! I do not think that the problem is in html tags, so I did not attach html code
Thanks for the help!

body {
    margin: 0 auto;
    width: 100%;
    height: 100%;
    background-color: #321de2;
}

#survey-form {
    display: flex;
    justify-content: center;
    align-content: center;
    flex-direction: column;
    width: 500px;
    height: 100%;
    background-color: #B7FF64;
}

Answer 1

Are you trying to align the shape itself with flexes? Not this way.
Flexes are given to the parent, that is, if the form is in a body, write the rules for the body.
And all children will listen to these rules.

Answer 2

Hello. Read the book The New Big Book of CSS by D. McFarland 2016 flex section

Answer 3

https://frontender.info/a-guide-to-flexbox/