WP plugin "Categories editor is optimized for desktop and not available on mobile"

The PeerBoard Community WP plugin "Categories editor is optimized for desktop and not available on mobile"

I'm on desktop, but I get the above error when clicking the Categories button. And my entire Peerboard looks narrow, as if it were on a mobile device. So it seems like the WordPress plugin is in "mobile" mode. I'm using the WordPress Twenty-wenty-One theme. Is there some configuration I need to do to fix this?