Github commits trigger build, but Travis never posts back to the PR

The affected project is

Also, maybe independently:

  • all repos on my account are marked as “legacy”
  • attempting to disable them fails, claiming an organisation permission issue, although this is not an organisation repo
  • there is no “big green button” as described in the upgrading docs for integration
  • the Travis app is not installed on my account or the repo, and Travis makes no request for it to be added.