Can’t get include tag to work

I’m trying to get my blog template to link to my main website header and footer pages, so that I can update them easily across the site. Using the same code as I use in the rest of the pages, it doesn’t seem to work (see https://www.atlanticrow2007.com/blog/ to see what happens – it’s right at the bottom).

I don’t have much idea what I’m doing and, after searching through these forums and the rest of the internet, I can’t work out where I’ve gone wrong.

Any ideas?

Thanks