How to fix : The error message includes a "Code: -51410" and a "Message: AADSTS900144 Description: (pii), Domain: MSAIMSIDOAuthErrorDomain." on Outlook for Mac?

Hi @DeboraFhrer-8208

Thank you for posting your question in Microsoft Q&A. 

It looks like you're experiencing an error in Outlook on macOS. I'm here to help. 

As my research, the error message with Code: -51410 and Message AADSTS900144 on Outlook for Mac indicates an issue with the authentication process. 

The error code AADSTS900144 indicates that your stored authentication token is either invalid, expired, or blocked due to a recent change in security policies. This typically requires you to sign in again. 

You can refer via: Microsoft Entra authentication & authorization error codes - Microsoft identity platform | Microsoft Learn 

If it possible could you try to follow these steps to troubleshoot it: 

1.Clear Outlook Cache:  

Quit Outlook. 

Go to ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook Preferences/ in Finder (use Command + Shift + G). 

Move files to a backup location, then relaunch Outlook and sign in. 

2.Updating Outlook and re-add your account: 

Go to Help > Check for Updates and install the latest version 

Then, open Outlook, go to Preferences > Accounts, remove the account, and re-add it. 

3.Contact your administration:  

Provide them the error details (Code: -51410, AADSTS900144, MSAIMSIDOAuthErrorDomain). 

Ask them to check Azure AD settings, MFA, or conditional access policies. There might be a misconfiguration in one of these areas that's affecting your account access. 

To help address your issue more effectively, could you please provide the following information: 

1.What is your current MacOS version? 

2.Did this issue start after any recent changes? (macOS updates, account changes)? 

3.Have you tried accessing Outlook via the web and does the issue still persist? 

Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution.

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