Notification from webhook

I have a simple notification policy to contact points(flask web server on the same virtual machine) based on labels in alerting( test_sensor=on, test_sensor=off). Sometimes grafana doesn’t trigger webhook, but the alert works well.
logger=alertmanager org=1 level=debug component=dispatcher aggrGroup=“{}/{test_sensor="off"}:{}” msg=flushing alerts=[test_sensor[1479d74][active]]
logger=alertmanager org=1 level=debug component=dispatcher receiver=test_sensor integration=webhook[0] msg=“Notify success” attempts=1
logger=alertmanager org=1 level=debug component=dispatcher aggrGroup=“{}/{ test_sensor="on"}:{}” msg=flushing alerts=“[ test_sensor below 90[558ddc4][active]]”
logger=alertmanager org=1 level=debug component=dispatcher msg=“Received alert” alert=" test_sensor below 90[558ddc4][active]"