Why can’t I see the alert rate estimate when tuning the alert settings?

As a rule of thumb, you can’t run simulation on a time scale smaller than the time scale the data is sent (e.g., if you’re sending one data point each hour, you won’t be able to see simulation for the 5 minutes time scale).
For different time scales, there’s a different minimum amount of data points that is required to run simulations. Consult our facts & figures for more details.
Also, the maximum number of points over which a simulation can be run is 5 million data points. Note that If the alert contains influencing metrics, they will be counted as well (and may affect the ability to run the simulation).