Grafana alerts by weekdays and weekends

Hello! I have a dashboard with query:
sum by(pro_key) (postgre_list_count{pro_key="QueryOrder"})
So, I need create grafana alert rule for it. I used for weekend threshold alert:
sum by(pro_key) (postgre_list_count{pro_key="QueryOrder", day_of_week=~"^(5|6)$"})
But when I press Run queries it displays: No Data, otherwise dahboard shows to me value.
Can you help what I need to do? Thanks.