Grandchild theme plugin issue.

I’m updating a website for a client, and they are using a child theme of the Cherry framework. I’m trying to use the grandchild plugin from here , and all was well until this last round of changes, and now css doesn’t show. When I look at the rendered page source it shows main-style.css from the child theme keeps listing lower than my plugin folders css and taking over. All the others from the child theme are above it except the one I’m trying to override. I’ve tried to uninstall the plugin and reinstall, reverted back to the blank plugin template and tried the same again. Nothing I do seems to make this thing work again. Any ideas?