Cover image not visible but present in css

I’m running a self-hosted instance of Ghost (v. 3.40.5) and using the Editorial template (v2.0). I have set the favicon image and it displays correctly, but the image uploaded for the publication cover does not. It appears in the Settings page, and if I look at the HTML I can see the .png file name in this < head > element (< meta property=“og:image” content=“” >)

The image does not display in the header as it should. If this is caused by an override is it possible for me to use code injection to fix it?