Alerts Work Some Days and Not Others

Hi Anonymous ,

For alerts in power bi, you should know that 

Alerts only work on refreshed data. When data refreshes, Power BI looks to see if an alert is set for that data. If the data has reached an alert threshold, Power BI triggers an alert.

Receiving alerts

When the tracked data reaches one of the thresholds you've set, several things happen. First, Power BI checks to see if it's been more than an hour or more than 24 hours (depending on the option you selected) since the last alert. If the data is past the threshold, you'll get an alert.
You mentioned that you had previously set a limit of at most every 24 hours, which may be why the alert didn't take effect, and I noticed that your 1/27 refresh start time to 1/28 refresh finish time was greater than 24h.

Best regards

Albert He

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly