When editing the alert: "MS SQL Always on Availability Group in Non Healthy State", the base object is empty and needs to be selected in order to save or make changes.
MS SQL Management Pack 9.1.x for Aria Operations 8.x
This is a known issue that will be corrected in a future release.
You can correct the Alert in 1 of 2 ways.
1) Download the attached .xml file and import the alert in the Alerts Configuration screen.
2) Go to Operations -> Configuration -> Alerts Definitions