Please try "HTTP/HTML request step" on behalf of "REST step" and set the "Host Name:", "Port:", "User:", "Password:" and "Path:"
Then add one post parameter which is suitable JIRA API
And change the "Form Encoding:" as "multipart/form-data; boundary=----".
I do not have the access for JIRA and JIRA REST API but I tried REST API in DevTest which would deploy .mar file to VSE and I could deploy the .mar file.
Here is the screenshot of the "HTTP/HTML request step" in my trial.
My trial and this screenshot may help you.