Alerting notification not working for some alerts

I created a dummy alert which should get triggered every 4 hours to test if alerting is working fine.
I configured a slack channel as contact point and the networkpolicy with the correct label and contact point.
When i test the contact point, i recieve a notification on the slack channel, but when the alert fires, the slack channel is not getting notified.
I am unable to figure out, why the notification for this particular alert not working.
Grafana version: v8.5.3 self hosted on K8s

The general notification policy which matches all alert instances, was probably blocking the test notification. After i created a nested policy inside the general one, the notification worked.

Not sure though why!