A Microsoft desktop and app virtualization service that runs on Azure. Previously known as Windows Virtual Desktop.
The error indicates that the deployment would exceed your Azure subscription's approved regional vCPU (core) quota. Although it appears to be a quota issue, the fact that the deployment succeeds intermittently with the Azure Virtual Desktop (AVD) Quickstart suggests there may also be temporary regional capacity constraints or differences in the VM sizes and availability zones selected by the deployment.
First, verify your regional vCPU quotas by going to Azure Portal > Help + Support > Quotas (or Subscriptions > Usage + quotas) and confirm that the target region has enough available cores for the selected VM size. If necessary, request a quota increase or choose a VM size that requires fewer vCPUs.
If sufficient quota exists, the issue may be due to limited capacity for specific VM sizes in the selected region. Try a different VM size within the same family, disable availability zones if they are enabled, or retry the deployment later. The Quickstart template may automatically select a different VM size or deployment configuration, which explains why it occasionally succeeds.
Since you already have a virtual network, storage account, and server in an existing resource group, review the Quickstart deployment settings to ensure it targets your existing resource group and virtual network. If Quickstart created resources in a different resource group, it was likely using its default deployment configuration rather than your existing infrastructure. Deleting partially created resources before retrying is also recommended to avoid conflicts from failed deployments.
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hth
Marcin