PowerBI API Returns "PowerBINotAuthorizedException" despite permissions

Hi - I am trying to access the API to download usage statistics from PowerBI and integrate with other reports. When I run the below code

import requests
import json

base_url = "https://api.powerbi.com/v1.0/myorg/admin/"
url = "https://login.microsoftonline.com/my_tenant_id_goes_here/oauth2/token"
scope = "https://analysis.windows.net/powerbi/api/.default"
grant_type = "client_credentials"
client_id = "my_client_id"
client_secret = "my_client_secret"
resource = "https://analysis.windows.net/powerbi/api"

header = {
    "scope": scope,
    "grant_type": grant_type,
    "client_id": client_id,
    "client_secret": client_secret,
    "resource": resource
}

r = requests.post(url, data = header)
login_result = r.json()
print(login_result)

token_type = login_result.get("token_type")
access_token = login_result.get("access_token")

authorization_key = token_type + " " + access_token
print('Authentication Key Generated')
headers = {'Content-Type':'application/json','Authorization': authorization_key}
print('Consuming Dashboards Rest End Point')
data = requests.get(base_url + 'dashboards', headers=headers)
print(data)
json_data = data.content
print(json_data)

 When I print login_result I get what seems to be a correct response.

{'token_type': 'Bearer', 'expires_in': '3599', 'ext_expires_in': '3599', 'expires_on': '1667296164', 'not_before': '1667292264', 'resource': 'https://analysis.windows.net/powerbi/api', 'access_token': 'longlongalphanumericstring'}

However when I print data I get a <401> error, and the json_data reads

b'{"error":{"code":"PowerBINotAuthorizedException","pbi.error":{"code":"PowerBINotAuthorizedException","parameters":{},"details":[],"exceptionCulprit":1}}}'

I have checked in Azure for the permissions. I have the Dashboard.Read.All permission.

Can anyone please let me know what I could be doing wrong?