Theme Customizer/Live Preview not working

In the theme customization page, I have the menu column on the left side, but the live preview area is blank.

This is true in all browsers, for all themes, and with or without plugins activated. This is a fresh install of WP.

I have tried a number of the “solutions” that were offered to those with the same problem for previous versions, but with no luck. I’m wondering if the problem is that I have my cpanel redirecting my homepage to the wordpress subdirectory (example.com redirects to example.com/wp). In any case, the problem makes the theme I’ve chosen pretty much unusable.

Any ideas?

(Be gentle. I’m the definition of ‘amateur’ where WordPress is concerned.)