Public project won't build, either by pushing or triggering a build

I’m currently having trouble getting this build to work.

I’ve tried to enable it in account settings, and it appears to be enabled under “Legacy Services Integration”. (I have no idea what this is or how it ended up there.)

Clicking “Activate & Migrate” just leads me to the settings page for the Travis-CI app in GitHub. (It is granted full access to all repositories in the organization.)

Any ideas?