Duplicated default.hbs but only footer content displaying?


I am new to Ghost and am attempting to customize Casper 2.6.3.

I copied default.hbs as custom-code.hbs to use as a sandbox page to experiment with hbs, js, etc. No changes yet, just copied the file and zipped up the theme. I added a navigation link via the desktop admin UI and the page loads, but only the footer content is visible. I would have assumed that this page would be identical to default.hbs.

Any ideas why the rest of the page is not rendering?

Thanks in advance.