error in child theme - Cannot modify header information - headers already sent

Hi,

I'm getting the following error message when using the child theme for Blogs MU:

Warning: Cannot modify header information - headers already sent by (output started at /var/www/vhosts/default-domain.com/httpdocs/wp-content/plugins/directory/core/main.php:517) in /var/www/vhosts/default-domain.com/httpdocs/wp-includes/pluggable.php on line 896

The child theme is showing the header but not the footer or the content (except for the search bar) see screenshot attached.

The main theme is network activated and I have moved the child theme from the main themes folder within the blogs-mu folder and placed it in the wp-content/themes folder - see attached screenshots

are there any more dependency files that also need to be moved into the child themes folder?