Can you provide the deployment or logs associated with this? So the note says "If the virtual machine plan is no longer available in the Marketplace, you can't use this procedure" are you sure that the offer is valid and available?.
Try this command to check
offer = Your offer in Marketplace offer=$(az vm get-instance-view --resource-group $sourceResourceGroup \ --name $vmName --query 'storageProfile.imageReference.offer' --output tsv)
Hope this helps.
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