css changes in child theme not working

css changes in enfold-child are not visible in frontend

I have uploaded enfold-child folder via ftp, but any change I make there is not visible in front end of the site. If I add a change in the extra css field in the customizer in WordPress CMS then the change will be visible.
For example: .footer_color {background-color: red;}

But adding css changes in the extra css files is not what I want. I would like to be able to use the enfold-child css folder.
Please help asap, I have looked several times at the support forum but no solution for me sofar.
Should I add lines to the php file too ? Now there’s only <?php

I have asked this question before but didn’t receive any help sofar.
I hope this time I’ll get support
Thank you

Kind regards
Alida