Azure Monitor CPU and Memory Percentage metrics stopped reporting for App Service Plan

The issue reproduces directly in Azure Portal Metrics Explorer and through the Azure Monitor CLI/API.

For the affected S3 Linux App Service Plan, both CPU Percentage (Average) and Memory Percentage (Average) show -- with no datapoints, even with Last 1 hour / 1-minute granularity.

At the same time, Data In returns 0 B, demonstrating that Azure Monitor is responding for the resource and other metrics are available.

The App Service Plan is healthy and in Ready/Running state with one Large worker, and the applications attached to it are running.

A comparable S3 Linux App Service Plan reports CPU and Memory metrics normally.

Please help why the underlying Azure App Service platform is no longer emitting CPU Percentage and Memory Percentage datapoints for this specific App Service Plan, and advise on a remediation that does not require recreating or unnecessarily modifying the production App Service Plan.