Custom header image

Hi

I created a test site on wordpress.com a year ago using the McKinley theme.

I am now trying to make the site live. I have organised hosting, have created a McKinley child theme, and am starting to recreate my pages. But under Dashboard > Appearance > there is no ‘Header’ custom header field to add pictures as there is on the WordPress.com site.

I saw the closed thread with this same name (11 months old) and tried adding the code suggested there to my child theme css but there’s still no opportunity to upload custom header images.

The host suggests it may be a different version of McKinley, is wordpress.com version different to a download just this week?

Is there a way I can restore this function?

Thank you
Stuart