Text box with redirect links has gone missing

In my admin area, on the plugin page (Settings > Redirect Editor), the large text box with all my redirects has mysteriously disappeared. It’s been like this for a few days.

The intro text on the page (down to the example redirect set off with “code” tags) is intact, but the textarea in which I can type is gone.

My previously added redirects still appear to work, so the plugin is otherwise functioning properly.

I’m using WordPress vers. 4.9.4 and Redirect Editor vers. 1.6.1.