Query Azure Resource Graph from Azure Monitor

Hi all,

I'm having an issue with this which I think is permissions related. Alert isn't firing even though the MI has reader access to Log Analytics and the resources I'm querying (see below) When I run the query it works fine.....

arg("").Resources 
| where type == 'microsoft.compute/virtualmachines'
| where tolower(tostring(tags.is_live)) == "t" or tolower(tostring(tags.is_live)) == "test"  // Send alert if the is_live 
| project TResourceID=tolower(id), tags 
| join (Heartbeat
    | where TimeGenerated > ago(12h)
    | summarize LastCall = max(TimeGenerated) by Computer, _ResourceId
    //| where LastCall < ago(15m)
    | where LastCall < ago(5m)
    | project
        HResourceID = _ResourceId
        ,Computer
        ,LastCall
    )
    on $left.TResourceID == $right.HResourceID
| project Computer, HResourceID, TResourceID,tags, LastCall

 Any ideas?