Trying to do POST API call to create a Github issue in jira

Getting 501 internal server error.
I have Provided the

{
  "fields": {
    "project": { "key": "ATFSD" },
    "issuetype": { "name": "Story" },
    "summary": "the new issue",
    "description": "The Github issue link is abc",
    "labels": ["bugfix", "enhancement"]
  }
}

could you guide us what is the issue