I have addressed this issue before, now I am down to brass tacks (crunch time).
We have a staging site that we have used for about 3 months to develop some custom stuff to add to an Enfold Theme WordPress site.
Meantime (since June), the live site has had numerous content updates. We are trying to merge the two.
I decided on this approach.
(1) I dropped all the wp- tables from the staging site database, then copied over the same from the live site, using phpmyadmin.
(2) The site now thinks it's using the base (not child) theme, but it recognizes that the child theme is there, I activated the child theme, I had to reset things like the logo, favicon, home page, etc. That was fine.
(3) If you use the Editor (Themes, Appearance), the CSS, functions.php & header.php are all there (as they were BEFORE copying over the DB tables), but it does not appear to be applying the CSS to the theme. The site appearance, once I recreate the child theme, is what looks like some garish color scheme, etc. I remember before when I first did that, it looked like that too.
Is there something I have to do to the child theme to make it use the custom css? I'm not sure if it's using the custom header & functions. How can I make that happen?