Virtual Machine Scale Sets: Metrics reporting stopped unexpectedly — Investigating data gaps

Problem description

I am experiencing a problem where metrics for my Azure Virtual Machine Scale Sets (VMSS) have ceased reporting starting at 01:14 UTC today. Specifically, in the Azure Portal, the charts for metrics such as Percentage CPU show no data for approximately 6.5 hours across all VMSS resources. I am seeking assistance to understand the cause of this gap and how to resolve it.

Environment

Azure Virtual Machine Scale Sets viewed through the Azure Portal metrics experience. The issue affects multiple VMSS resources rather than a single instance. Specific region, SKU, operating system, deployment model, or resource identity are not specified in the case information.

What I've already tried

I have checked whether metrics are being emitted for the selected time range, widened the time range and increased granularity, verified that the Microsoft.Insights resource provider is registered, confirmed I have the necessary permissions, and used PowerShell and the REST API to read metrics outside the portal chart. However, these steps did not resolve the issue.

Current status

The metrics gap persists, and I am trying to determine whether the missing data is only a portal display issue or also absent from the underlying metric stream. I am also interested in understanding if any changes occurred around the time the gap began and what potential troubleshooting steps I should take next.

This is occurring on all our Virtual Machine Scale Sets across multiple subscriptions.