What theme was initially active? Please check your child theme’s style.css heading which typically look like this.
Theme Name: Perth
Theme URI: http://athemes.com/theme/perth
Author URI: http://athemes.com
Description: Perth is a business theme suitable for both companies and freelancers. Easily create an strong online presence by taking advantage of the many construction blocks available in Perth, like services, employees, skill, social and much more. Also, Perth provides an extensive set of options, including color and font control.
License: GNU General Public License v2 or later
License URI: http://www.gnu.org/licenses/gpl-2.0.html
Text Domain: perth
Tags: light, two-columns, right-sidebar, fluid-layout, responsive-layout, custom-colors, custom-background, custom-header, custom-menu, featured-images, sticky-post, theme-options, threaded-comments, translation-ready
This theme, like WordPress, is licensed under the GPL.
Use it to make something cool, have fun, and share what you've learned with others.
Perth is based on Underscores http://underscores.me/, (C) 2012-2015 Automattic, Inc.
What is the Template line value?