Mantra Theme – Header upload page disappeared

I have used Matrix on several sites so I know it quite well. On this newest website I’m developing, the header upload page has disappeared. When I uploaded the first header, there was no problem. But when I went to upload a replacement header, the page is empty. The only thing that is on the page is a Save & Publish button on the top left, and below that, it says You are customizing karaohs WordPress. There is nothing else on the page, it is completely blank.

I deleted the image for the first header, thinking that would get me back to the page where I can upload a new image, but now I have no header image, and no way to fix the problem.

Thank you for any assistance you can give me.

Kara Oh