Header background image not displaying after upgrade to 4.3.1

Hello!
After moving my client’s website to a new ISP and reinstalling it in the latest version of WordPress plus Enfold 4.3.1, I cannot get any kind of image to display in the background of the header behind the logo. Choosing one of the default backgrounds doesn’t work, neither does uploading the site’s custom image through the theme options interface. The image appears in the preview of the theme options, however. It has definitely uploaded.

You can see the no-show at the temporary address (see private content). Compare this with the original version (see private content).
I have searched the forums and tried the suggested approaches. Nothing seems to work. Any ideas?
Only plug-ins installed are “duplicate post” and “search exclude”, neither of which are causing problems with this setup on other sites I run.

Many thanks