Hi @Greg H , according to this document:
When you use Azure Resource Manager for email notifications, you can send email to the members of a subscription's role. Email is only sent to Microsoft Entra ID user members of the role.
Please make sure that your Monitoring Readers role is set at the subscription level, not at resource group or any other level.
Please accept an answer if correct. Original posters help the community find answers faster by identifying the correct answer. Here is how.