Hello!
We just tested POST call for device status from POSTMAN, and it's working just great.
Make sure in your script you are using the right parameters for cURL and POST.
For PHP for example use "curl_setopt($ch, CURLOPT_POST, 1);", if instead is used "customrequest".
And send the data for "curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($data));"
Note that, if the POST is working from another software, then the cloud logic on the Shelly side have no issue.