Changelog Service Not available

While trying to access changelog api via{issueIdOrKey}/changelog-getChangeLogs, it’s returning HTTP1.1/ Service Unavailable. While digging into it, a new version of JIRA returns the content perfectly fine.
In the api documentation, it has been mentioned that if the user doesn’t have access or the issue is not available it would return 404. What permissions have to be set up to make this api available? Is it something related to Jira version or just the permission issue?

Service unavailable is typically an HTTP 503 error code, and indicates that an error occurred on the server at which your request was aimed. Not sure what that might be, but check that the body of the HTTP response doesn’t have something helpful in it.

The user would need BROWSE_PROJECTS permission for the project containing the issue in question; otherwise you’ll get an HTTP 404, which is not the same as the HTTP 503 mentioned above.