I have converted site from http to https and it's on AWS instance. It breaks the CSS, seems that relative CSS and JS URLs are not considering the HTTPS scheme and take HTTP.
Check your settings, and make sure you don't have something hard-set to http. If you're using a custom style, do a template search and remove anything with http://
@motowebmaster Nope there's nothing hard coded, I looked everywhere. Not sure, but the issue is that, it's considering relative css.php URLs as HTTP, wondering.