As with most things in SCOM/SquaredUp, it’s all about choosing the correct object, and the server itself is surprisingly not the one here.
You should be using the Health Service Watcher objects:
To understand why you should use the watcher objects, think of it like this: When an agent goes offline, how does it tell SCOM that it’s offline when it’s offline? The simple answer is that it doesn’t. There’s a check against all agents from the SCOM management server every 60 seconds (see: Health Service Heartbeat), and there are monitors that check this heartbeat to make sure it responds.
If you scope a tile to the class shown above, you will only see these objects go into a critical state when SCOM loses contact with an agent, and you can filter this further to only show offline servers using the Criteria:
The above example is for a status tile, though you can use the Alerts tile with criteria for the alert names: