Solution

The datastore usage alarm will not re-trigger if it has already been triggered and manually reset to a green status when the datastore usage does not subsequently drop below the warning threshold percentage defined on the alarm.For example, if the warning threshold is set to 80% and the critical is 90%, the alarm will first trigger when the datastore reaches 80% capacity. If a user resets the alarm to green at this point, it will NOT trigger again, even at the 90% threshold, until the actual datastore usage drops below 80%.This is currently working as designed outlined by VMware engineering.