Execute DAX via. app registration and Power BI Rest API

Hi community

Has anyone ever tried querying Semantic model in Fabric using Rest API and an app registration (service principle) using the client id and a secret?

I am trying to use the “Datasets – Execute Queries” Rest API to execute DAX statements. I know the optimal way is semantic link library which works great but I have users not inside Fabric that are asking for access to run DAX (the long term plan is to get them inside Fabric but not an option in short term). I have tried the API out using Microsoft GUI “try it” (Datasets - Execute Queries - REST API (Power BI Power BI REST APIs) | Microsoft Learn) which works fine. However if I try to test this API in a Fabric notebook (I know – seems counterintuitive as we should use semantic link -  but it is just for a test) I cannot get it to work with an app registration.

I get this error when calling the API which offcource indicate some authentication problem – however I am not sure of what I am missing (my code example at the end in the post):

Error:

Response status code: 401 {'error': {'code': 'PowerBINotAuthorizedException', 'pbi.error': {'code': 'PowerBINotAuthorizedException', 'details': [], 'exceptionCulprit': 1, 'parameters': {}}}}

I have checked the following.

1. The workspace of the  semantic model is backed up by premium capacity (F128)
2. The app is admin in the workspace with the model
3. In the tenant setting both “allow service principals to call Fabric public APIs” and “Semantic Model Execute Queries REST API” is enabled for entire organization.
4. The service principle has been grandted Dataset.ReadWrite.All as of “delegated” type under API permission on the app registration. Admin consent has been granted.
5. I have tried getting a token from both 'https://analysis.windows.net/powerbi/api' and “https://analysis.windows.net/powerbi/api/.default. Same error message

My test code from a notebook

#Test DAX via. Rest API
#Datasets - Execute Queries - https://learn.microsoft.com/en-us/rest/api/power-bi/datasets/execute-queries

import requests
import invest_azure_fnk as iaf
af = iaf.azure_functions()
from pprint import pprint


# access token via. team data solutions app
access_token = af.get_access_token(resource =  'https://analysis.windows.net/powerbi/api') #custom library that can return an access_token for a given resource
#print(access_token)


url_test= F"https://api.powerbi.com/v1.0/myorg/datasets/74823857-dd72-41e9-8e01-7d548e28e61a/executeQueries"


# Headers 
headers = { "Content-Type": "application/json"
    , "Authorization": f"Bearer {access_token}" }

body = {
    "queries": [
        {
            "query": "EVALUATE VALUES('CALENDAR'[YEARNUMBER])"
        }
    ]
}


# Make the GET request 
response = requests.post(url_test, headers=headers, json = body) 
print('Response status code: ' + str(response.status_code))


try:
    pprint(response.json())
except:
    print('cannot print response as json')