Hello,

Are you using a child theme? By default the child theme calls first the style.css file you have in it. There is no need to alter functions.php file. Just add the custom style in your child theme’s style.css file.
You can read more about it here: https://codex.wordpress.org/Child_Themes

Best regards!

Hello,

Do you have any caching service set up in your server? Please flush the server cache first. So the new copy will be loaded and display.
Let us know.

Best regards!