Hello,@coze,
Welcome to the Microsoft Q&A platform!
Based on your description, I understand that you received an error message that the user account does not exist in the directory when you authorized with Email Oauth. This is related to your Azure Active Directory account. To begin with, I would like to confirm with you whether you have a local IT or global administrator status.
If you are a local IT or global administrator, you could search this website for reference on the error code: Microsoft Entra authentication & authorization error codes - Microsoft identity platform | Microsoft Learn. For your convenience, I have taken a screenshot of the error code and the reason below.
For more information and solutions, please refer to this document: Add B2B collaboration users in the Microsoft Entra admin center - Microsoft Entra External ID | Microsoft Learn
Suppose you do not have the status of an administrator, to solve your problem, I suggest you contact your local IT or Global administrator who is handling your Azure Active Directory (AAD) tenant to ensure that your account was successfully added.
If my reply is helpful to you, please mark it as the answer so that other users can refer to it. Thank you for your support and understanding.
Best,
Alex Zhang