Alert condition occurring alert state is "pending" but return back to "Ok" state

I wrote 2 alert queries with flux and data is written every 1 hour (|> aggregateWindow(every: 1h, fn: sum, createEmpty: true)

Alert conditions are occuring but after “pending” state it return back to “Ok” state.
All rules in the selected group are evaluated every 15m and pending period is 35m.

What can be the reason of alerts not to fire ?


Versions: Grafana v10.1.1 / InfluxDB v2.7.1 with flux queries