Gmail loads and logs in, but no longer displays the rows of email items

At some point I have disabled a feature that allows Brave to display the lines of emails within Gmail. I can still log into Gmail and I can see the various mailboxes listed vertically on the left. But when I click any of them, there is just blank space in the main workspace.

“Add-ons” such as Calendar, Keep and Tasks all still work.

What have I switched off?

I don’t know how to reproduce this as I don’t know what setting has been changed.

The expected result is to be able to view lines of emails again.

v. 1.80.120

Additional info: I know this is something I switched off as I was fumbling around in the settings.