Alert Test Rule fails with working Teams Channel

Hi

I’m testing MS Teams webhook for alerting in Grafana v8.4.2.
I created a webhook and successfully sent a test alert to the MS teams channel.
However, when I try to add an Alert for a chart, and click on Test Rule, it fails

{
“firing”: true,
“state”: “pending”,
“conditionEvals”: " = true",
“timeMs”: “2.512ms”,
“error”: “request handler response error {client_error: client error: 401 A 0xc00084f110}”,
“logs”: [
{
“message”: “Condition[0]: Query”,
“data”: {
“from”: 1667480386827,
“queries”: [
{
“refId”: “A”,
“model”: {
“datasource”: {
“type”: “prometheus”,
“uid”: “”
},
“exemplar”: true,
“expr”: “sum(rate(apiserver_request_total{job="apiserver", code=~"2…"}[5m]))”,
“interval”: “”,
“legendFormat”: “”,
“refId”: “A”
},
“datasource”: {
“id”: 3,
“name”: “”
},
“maxDataPoints”: 1500,
“intervalMs”: 200
}
],
“to”: 1667480686827
}
}
]
}

Please guide on what could be the reason, and let me know if more info is needed