Hi there,
there isn’t anything in GP that would affect the behaviour of that plugin. I would assume the plugin is adding code to core WP hooks which again GP has no awareness of or control over.
If you know where the code needs to be added you can use a Hook Element:
https://docs.generatepress.com/article/hooks-element-overview/
There are 3 main hooks for adding scripts to WP:
wp_head – inside the <head></head>
wp_body_open – immediately after the opening <body> tag
wp_footer – in the footer
For ad placement codes there is a number of Theme hooks which you can see in the visual guide:
https://docs.generatepress.com/article/hooks-visual-guide/