I think I see what the issue may be.
If all servers cross the threshold at or near the same time, then they are all going to be blended into one incident.
Therefore you’ll only get one set of notifications.
As soon as the first server crosses your threshold, it creates an incident. While that incident is still open, any servers that cross the threshold after that will be rolled up into that incident.
This is because your Incident Preference setting is set to
By Condition. So any violation of the condition rolls up into the open incident for that condition.
If you want new incidents (therefore new notifications) for each server, you will need to change the incident preference setting to
By Condition and Entity
You can change the incident preference in the upper right of the alert policy page