Child theme help for Nelo- changes not showing on site

I am having trouble with the child theme. I renamed lib/css/child-style-sample.css to child-style.css as instructed to use the child theme, but my changes are not being implemented. I've been through the forums and tutorials...just not getting it to work (it's worked for other WPMU themes...just not this one). Any tips/suggestions would be greatly appreciated.