Exposed HTML artifacts only render for some projects

Hi, we have enabled Gitlab Pages on our self-hosted CE Gitlab instance so that viewing exposed HTML artifacts is more convenient.

You can expose an HTML artifact (e.g. a test report) like this:

  stage: build
    - echo "Hello world"
      - result.html
    # Add a link in the MR.
    expose_as: 'CI Report'
    when: always

Without Gitlab Pages, when you click on it:

It prompts you to download it, which is quite annoying:

However if you enable Pages, then it will host it on a web server and serve it for you. There is an annoying redirect warning page but you can disable that in very recent versions of Gitlab.

My issue is that it works for one project, but for a different project I get the above error. I’ve looked through the project settings and they are both identical as far as I can tell.

What could be causing this difference in behaviour? Can the configuration for build artifact storage vary between projects and be causing this issue?

Unfortunately I’m not an instance admin so I can’t see all the settings…