Hello,
Trying to send email from on behalf of user however getting below error.

I have added creator of this app in Mailbox permissions of "Service" user as you can see in the picture below.

Here is my code, Is there anything i am missing here.
Office365Outlook.SharedMailboxSendEmailV2("services@onmicrosoft.com", "RequestorUser@onmicrosoft.com", "This is a test", "Email Test Body")
Please help,
Thank you!
Aman