Goal: I want to get notified when ESXi host stops responding.

So, I created an item (from the template btw) called every minute:
vmware.hv.uptime[{$URL},{HOST.HOST}]
which works fine - I can see latest data being updated precisely.

Then I created a trigger:
{Vmware ESXi host:vmware.hv.uptime[{$URL},{HOST.HOST}].nodata(5m)}=1
Which is OK as long as the ESXi host is UP and running.

Once I shut down the ESXi server, the trigger status changes to UNKNOWN and it fails with following message:
Cannot evaluate function "...UUID...:vmware.hv.uptime[{$URL},{HOST.HOST}].nodata(5m)": item is not supported.

Unfortunately, nothing happens.