“We strongly recommend to use the PRO theme as it is because the child theme is not works properly.
If you are getting any problem in customizing the theme, you can contact us at any stage of your website development process. We are always ready to help you.”
If anyone else is thinking of Child theme it only will work for the free version of BuildUp. The paid version (BuildUp Pro) is no accepting a child theme. Guess I just have to roll with it. Hope this helps others.