Drupal 6 to 8 migration runs, but no text from nodes is displayed

I ran the Drupal 8 migrate function on my Drupal 6 database. It completed successfully. All the nodes appear to be there in the new Drupal 8 site. However…

None of the text is displayed. Only the titles. This occurs on all pages, regardless of type. The front page itself has no text other than the title.

I can edit a node and see the text from the Drupal 6 site there, available for editing. But when I save it, it still does not display.

I can add a new node with “Testing new site…” or some such in the body text. THAT does get displayed after saving.

The Drupal 6 site I migrated from was v.6.38, the last available version.

The Drupal 8 site I migrated into was v.8.3.6.

Any suggestions/advice?

Drupal version: 

Source: https://www.drupal.org/taxonomy/term/21/feed