ACS50012: Authentication failed

Hi,

I have a really strange issue with"/oauth2/token" endpoint (grant_type: "client_credentials")... A few days ago it doesn't work anymore (the endpoint for that app has worked fine for ~6 months):

Request (HTTP POST https://login.windows.net/{MY_TENANT_ID}/oauth2/token?api-version=1.0)

{
  grant_type: 'client_credentials',
  client_id: {MY_CLIENT_ID},
  client_secret: {MY_CLIENT_SECRET},
  resource: '00000002-0000-0000-c000-000000000000/graph.windows.net@{MY_TENANT_ID}'
}

Response (HTTP 400)

{"error":"invalid_client","error_description":"ACS50012: Authentication failed.\r\nTrace ID: d96a48f7-8438-4e4c-b07d-e78467536a7f\r\nCorrelation ID: ae3f89e7-741c-430b-966f-d471ddc7129b\r\nTimestamp: 2014-11-17 15:51:47Z","error_codes":[50012],"timestamp":"2014-11-17 15:51:47Z","trace_id":"d96a48f7-8438-4e4c-b07d-e78467536a7f","correlation_id":"ae3f89e7-741c-430b-966f-d471ddc7129b"
}

Also, I tried creating a new app (always from Azure portal) but I'm getting the same error.

Any ideas? Thanks!