REST API Execute rejects all commands Follow

I've successfully being able to fetch issues using REST API but the update of issues always fails with the invalid command error message, e.g.

{"value":"Command [State Fixed] is invalid:"}

I've tried to use PostMan and Node.js (I'm quite novice). I've tested the used commands also in the browser and they are working ok.

Below is the example used from Node.js:

options = {
headers: {accept:'application/json', authorization:'Bearer perm:<my-perm-key>, 'Content-Type':'application/x-www-form-urlencoded'},
body:'command=State Fixed'
}

res = req('POST', 'https://<my-domain>.myjetbrains.com/youtrack/rest/issue/<my-issue-id>/execute', options);