Header Missing after installing GTM code

I’ve customised everything on my site using the Twenty Seventeen theme and is happy with it. Tried installing the GTM code using several methods but the header image/video disappears as soon as I do. Any suggestions, please?

For installation of GTM I tried the following:
1) Header and Footer plugin
2) Header, footer and post injection plugin
3) Creating a child theme (via Child Theme Configurator) and added the code to the .php file.

• This topic was modified 6 years, 2 months ago by mickylinqy.

The page I need help with: [log in to see the link]