header not available or deleted when child theme just created

Hi

I am using this theme’s child theme for my site, I have practiced editing in staging twice, but on the second time, I accidently deleted I think the header part when ‘edit page’ shows ‘this area does not work without pagelayer, you can leave it or deleted”, I saw no code in there so I deleted, then header disappeared.

Then I went on to create another staging site, installed Zeever, use exactly the same method which is the Child Theme Configurator to create a child theme, just like how I did it in previous two time. But, everypage including front page, home page, no header, it says’ Template part deleted or not available: Header.

I thought it was a glitch, so I went on created another child theme with different name, same, header not there.

What did I do wrong? How can I create a child theme without missing template part?

Urgent, thank you

Jo