/merge REST API failed but PR got merged

I have an organization repo with master as a protected branch.

When I hit /merge REST API with Action’s default GITHUB_TOKEN, the API returns “You’re not authorized to push to this branch. Visit https://help.github.com/articles/about-protected-branches/ for more”, but the PR does get merged (verified by checking the PR’s page).

The PR is raised from release branch to master.

master’s branch protection settings:

merge commit created by Action:

Hi @vibin,

I followed your branch protected rule to create my own, and use rest api with GITHUB_TOKEN for check, the pull_request is successfully merged.
My workflow: https://github.com/weide-zhou/ticket13/runs/729930762?check_suite_focus=true
My pull_request:https://github.com/weide-zhou/ticket13/pull/104

Is the rest api command same with yours?
I also notice you use circleCI as a required status check, could you please change it to existing github workflow instead for a check?