Azure Monitor Agent not initializing or connecting to LAW for specific Production VMs deployed via Bicep module

Hello Vaibhav Anand, 

We understand that you're having trouble with the Azure Monitor Agent (AMA) not connecting for some of your Production VMs.

Since Non‑Prod works, some Prod works, but Prod WebApp VMs don’t connect (and one Prod RM VM flipped to Not Connected), this smells like a connectivity/association or rule/region mismatch rather than a generic AMA install problem.

1. Verify DCR region and DCRA association:  DCR created in a different region than the workspace, or DCRA not attached to the specific VM resource.

      # DCR and region
      az monitor data-collection rule show \
        --name <dcr-name-prod> --resource-group <rg-monitoring> -o tsv --query "location"
      # Workspace region (should match DCR)
      az monitor log-analytics workspace show \
        --workspace-name <law-name> --resource-group <rg-monitoring> -o tsv --query "location"
      # List associations for the VM
      az monitor data-collection rule association list \
   

   If region mismatch exists, redeploy the DCR in the workspace’s region. Microsoft explicitly requires this. Ensure each affected Prod VM has at least one DCRA to the intended DCR. Remember the many‑to‑many rule; wrong DCR > no data. Create data collection rules (DCRs) in Azure Monitor - Azure Monitor | Microsoft Learn Data collection rules in Azure Monitor - Azure Monitor | Microsoft Learn
2. Verify the extension is healthy on the Prod WebApp VMs:

      # Extension presence & status
      Get-AzVMExtension -ResourceGroupName <rg-prod> -VMName <vmname> -Name "AzureMonitorWindowsAgent"
       
      # Local Windows service state
      Get-Service -Name azuremonitoragent
   

   You should see the AzureMonitorWindowsAgent extension Provisioning succeeded and the azuremonitoragent service Running. If not, reinstall the extension (uninstall > install). This is the first set of checks in Microsoft’s AMA guidance. Install and Manage the Azure Monitor Agent - Azure Monitor | Microsoft Learn Troubleshoot the Azure Monitor agent on Windows virtual machines and scale sets - Azure Monitor | Microsoft Learn
3. Verify AMA Installation: Check the status of the AMA installation on your VMs. Run the following command:

      $vm = Get-AzVM -ResourceGroupName <YourResourceGroupName> -Name <YourVMName> -Status
       if ($vm.extensions) {
       Write-Output "Listing all VM extensions:"
       $vm.extensions | ForEach-Object {
       Write-Output "Extension Name: $($_.Name)"
       Write-Output "Type: $($_.Type)"
       Write-Output "Provisioning State: $($_.statuses.code)" 
       Write-Output "---"
         } 
          } else {
                 Write-Output "No extensions found for this VM."
                 }
   

   Ensure that the AMA extension appears with a suitable provisioning state.
4. Check Heartbeat Data: Run a query in Log Analytics to see if you’re receiving heartbeat data. Use:

      Heartbeat | where Computer contains "<your-computer-name>"
   

   If you see no data, the agent is likely not communicating with the Log Analytics workspace.
5. Confirm that your VMs can reach the required Azure endpoints. You can test connectivity using PowerShell:

      Test-Connection monitor.azure.com
   

6. Ensure there are no network restrictions, such as firewalls or proxies, that might be blocking the necessary Azure endpoints for AMA operation. Confirm DNS configuration and allowlist the URLs required for communication.
7. Look into the log files located at C:\WindowsAzure\Logs\Plugins\Microsoft.Azure.Monitor.AzureMonitorWindowsAgent to see if there are any errors that might provide more context.

If you still encounter an issue, could you provide more details regarding the following?

• Have you checked the Azure Monitor Agent's logs for any specific error messages?
• Is the Data Collection Rule properly configured with the correct resources?
• Are all your VMs in the same network setup, or are there differences (like different VLANs)?
• Have you made any recent changes in the environment or updates that could affect the connectivity?

Reference document:

Microsoft Defender for Cloud troubleshooting guide - Microsoft Defender for Cloud | Microsoft Learn

Hope this helps, If you encounter any issue, please do let us know. thanks