Zephyr Cloud API - automated creation of execution

Dear Community,

I'm new to Zephyr cloud so pardon is the issue seems obvious to you.

I've been using the ZAPI to certain endpoints as described in the documentation so far successfully but encountered a problem with some.

A most import feature we would like to implement is automated creation/update of test execution, not by a test manager, but ourselves using the code itself at the SetUp/TearDown stages of the test.

For this end I've been using the "Create Execution" and "Update Execution" APIs.

I was using them them same way I've been using the other endpoints and according to the documentation, but for the execution creation I have been receiving an error:

Internal Server Error{"errorType":"ERROR","clientMessage":"We encountered some problems during processing this request. Please try again!","errorCode":104}

Searching the web I've seen this error has risen more than a couple of times and probably having something to do with the JWT generation but I'm not certain of that as i've followed the instruction for JWT generation to the letter.

the URL for request (GET):

https://prod-api.zephyr4jiracloud.com/connect/public/rest/api/1.0/execution

request headers:

{
"Authorization": "JWT eyJ0...Xu0I",
"Content-Type": "application/json",
"zapiAccessKey": <Zephyr access key>
}

request body (json):

{"status": {"id": 1}, "projectId": <project_id>, "issueId": <issue_id>, "versionId": <version_id>}

having said that, I must emphasize that the update execution API does indeed work when manually creating the execution using the UI and just updated the execution with the executionId. 

Sincerely hoping for some intake on that.

edit: neglected to mention that trying to use the "try it now" console option from the official documentation  with the example body and default headers, yields the exact same results -  error 104 (https://zfjcloud.docs.apiary.io/#reference/execution/add-tests-to-folder/create-execution?console=1)