Adding responsive.css file to child theme….

This one is probably me doing something very basic, but wrong.

I have downloaded and am using the sample child theme from the hueman site. It’s activated.

I have added a function to the functions.php to fix a problem. (sharing posts to facebook wasn’t also sharing the featured image, needed to add some info to the headers of posts. If the author reads this, maybe its something that needs fixing?) Anyway the new function in the child themes functions.php works as it should.

However the other change I wanted to make, was in the responsive.css file. I was making some tweaks to when the sidebars disappear on small screens.
If I make the changes on the original themes responsive.css, it works as it should. But I dont want to do that, I want to make the change on the child theme.

So I make a responsive.css file in the child theme, copy the whole of the old respnsive.css contents into it, and make the changes I need.

but on the site, nothing happens. No matter what I do, the Original responsive.css file is what is always used. The one I have in the child theme is ignored.

I’ve done googling and whatnot, and tried a few things, but as far as I can tell I have the files set up correctly… something somewhere is just causing my child theme file to be bypassed.

The style.css in the child theme seems to be working as it should, as is the functions.php (as I said before).

Hopefully this is enough info for someone to give me a hint as to where I’m going wrong!