The Zerif lite seems to be removed from wordpress theme lists.
I am using same theme for my business page.
The theme is unlisted from www.ads-software.com, however the developers still offer it on their website. The solution to above all issue is to download a new copy from their website and replace the zerif-lite theme folder with new version.
Make sure to backup your old theme folder before replacing it. And yes this will work only if you are using child theme for your customization.