Can't merge site header when using Elementor

Hi,

I am creating a homepage with Elementor and need to merge it with the site header.

I have created a header element, enabled the merge with content setting and assigned it to the front page using the display rules. No matter what I try, the header always displays with a white background (even though it is set to transparent).

Can you help? I've done this before using Beaver Builder and seem to remember it being straightforward, but just can't get it to work with Elementor.

Thanks!