How to make a check fail

Hi there,
I’m making a simple GitHub Action for checking code coverage.

At the beginning of the (Ruby) script, I create a check vai the /repos/{owner}/{repo}/check-runs GitHub API.

Here is the body of my POST request:

 {
      name: 'Code Coverage',
      head_sha: SHA,
      status: 'in_progress',
      started_at: Time.now.iso8601
  }

After verifying the code coverage, I update the check by making a PATCH request to /repos/{owner}/{repo}/check-runs/{check_run_id}

Here is the body of my request:

{
      name: 'Code Coverage',
      head_sha:SHA,
      status: 'completed',
      completed_at: Time.now.iso8601,
      conclusion: 'failure',
      output: {
        title: "Code Coverage 0%",
        summary: 'YOU HAVE FAILED',
        annotations: []
      }
    }

However, the check in my PR doesn’t fail.

Am I missing anything here?
Shouldn’t conclusion: 'failure', make the check to fail?

Thanks,
Sig