Flat Responsive theme responsive except for header

Hi! I’m using the free version of Flat Responsive and, although the content does respond on mobile/tablet/desktop, the header image does not. I wanted to test this theme out before upgrading to pro but, if the header isn’t responsive, then I would rather not spend the money.

I’ve tried using the ‘banner wide’ widget instead as I saw suggested elsewhere but this doesn’t work (it is just a teeny little banner in the top left corner of the header rather than a site-wide image – not sure if that’s what it’s supposed to look like?).

I’d really appreciate your insights, thank you!

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