"Authentication Failed. Access is Denied for the provided Azure Organizational Account Credentials" - Error message upon adding a New Azure monitor using Azure Organizational Account mode.
Troubleshooting:
Check if the provided User Email & Password fields are correct by logging into portal.azure.com using the same credentials. The password might have expired or this is the first time the user is logging with these credentials.
In this case, the user has to change the password and provide the updated password while creating a new Azure monitor.