No Content Found after moving staging site to live site

Slidedecks we created on a staging site are all working fine, but after we moved the staging site to the live site, it’s impossible now to create a new slidedeck using the custom option for populating it with images from the media library.

It “creates” and saves the deck, but then there’s nothing but this:

NO CONTENT FOUND
We’re having trouble finding your content. Please double-check
your source configuration at the top of the page.

One problem is that there is no “source configuration at the top of the page” to check.

Clicking on the first slide to try to choose an images does nothing. It just sits there dead.

Please advise.