PowerBI API - Execute Queries on Dataset - Problem with DAX Statement

Good morning,

i am not able to execute any queries via the Execute query REST API, except when i ONLY use evaluate.

As you can see this one works without problem:

{
"queries": [
{
"query": "EVALUATE VALUES(Manufacturer)"
}
],
"serializerSettings": {
"includeNulls": true
}
}

RESULT:

{
  "results": [
    {
      "tables": [
        {
          "rows": [
            {
              "Manufacturer[ManufacturerID]": 6,
              "Manufacturer[Manufacturer]": "Leo",
              "Manufacturer[MfgisVanArsdel]": "No"

But when i literally use any other query like this:

{
"queries": [
{
"query": "AVERAGE(Sentiment[Score])"
}
],
"serializerSettings": {
"includeNulls": true
}
}

The Result usually shows something like:

{
  "error": {
    "code": "DatasetExecuteQueriesError",
    "pbi.error": {
      "code": "DatasetExecuteQueriesError",
      "parameters": {},
      "details": [
        {
          "code": "DetailsMessage",
          "detail": {
            "type": 1,
            "value": "Query (1, 1) The syntax for 'AVERAGE' is incorrect. (AVERAGE(Sentiment[Score]))."
          }
        },
        {
          "code": "AnalysisServicesErrorCode",
          "detail": {
            "type": 1,
            "value": "3238920194"
          }
        }
      ]
    }
  }
}

I would appreciate any kind of help or hint in what i am doing wrong, or if certain statemeent s are just not supported within the API etc.

BR Ruben