Thanks Sérgio,

It was custom fields. We had a custom field in our Jira that prevented the call. I had to use the JUnit multipart api to get that sorted.

/ # curl -H "Content-Type: multipart/form-data" -X POST -F [email protected] -F [email protected] -F [email protected] -H "Authorization: Bearer $TOKEN" https://xray.cloud.getxray.app/api/v1/import/execution/junit/multipart
        {"id":"16736","key":"PRJ-199","self":"https://mydomain/rest/api/2/issue/136"}/ 
  #

So I ended up these information passed in from testIssueFields.json and testExec.json Thanks!