My account no longer exists?

Hi @Matthew Betteto,

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

The error AADSTS900561 typically occurs when the authentication request is sent using the wrong HTTP method. Azure AD requires POST requests to process tokens and sensitive credentials, but in this case, it received a GET request instead. One of the most common causes is that your browser may be blocking third-party cookies, which are essential for the authentication flow to complete successfully. Another possibility is that your browser’s cache or cookies are outdated, which can interfere with session data and lead to unexpected behavior. Sometimes, certain browser extensions might also disrupt the authentication process. 

You can try the following steps to help with your situation: 

1.Enable third-party cookies 

Could you please let us know which browser you're currently using? Here's how to allow third-party cookies for Chrome and Edge: 

• Chrome:  Go to Settings > Privacy and security > Third-party cookies > Select Allow third-party cookies 

• Edge: Go to Settings > Privacy, search, and services > Cookies > Turn off Block third-party cookies

Note: If you are using other browser, please comment to let me know.

2.Clear browser cache and cookies 

• Clear all cached data and cookies from your browser. 
• Alternatively, try accessing the site using Incognito/InPrivate mode. 

3.Add login URLs to Trusted Sites 

• Open Internet Options 
• Navigate to the Security tab > Select Trusted sites 
• Add: https://login.microsoftonline.com and any other Microsoft endpoints you use 

4.Try a different browser or device: This can help determine if the issue is browser specific. 

However, if the issue persists, I'd recommend you to reach out to Microsoft Support team via 2 following methods. You can find the appropriate phone number using this link: Customer service phone numbers – Microsoft Support.

For security and privacy, all investigations into account issues are handled exclusively by our dedicated Microsoft Data Protection team. As moderators, we do not have access to the systems. We also do not have the capability to initiate remote sessions for direct assistance. Our role is to guide users to the appropriate resources and support channels. 

If you still cannot reach to a live agent, there is still a workaround, you might consider registering for a new tenant by signing up for a trial subscription via this link Microsoft 365 Business Plans and Pricing | Microsoft 365. This would allow you to create a new tenant following the prompts provided. Once set up, you can access the admin console of the new tenant and submit a support ticket requesting to speak with the Data Protection team on behalf of your previous tenant.

In the Microsoft 365 Admin Center > Support > Help & Support. You can raise support ticket at https://admin.microsoft.com/#/support/requests    

Please remember to cancel the trial subscription once your issue is resolved to avoid any unintended charges. 

For your security, please do not reply to this thread with this card information. The official support line is the only secure way to handle these details. 

I hope this information is helpful. Please follow these steps and let me know if it works for you. If not, we can work together to resolve this.    

Thank you for your patience and your understanding. If you have any questions or need further assistance, please feel free to share them in the comments on this post so I can continue to support you. 

I look forward to continuing the conversation. 

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Thank you for your response. I have followed all of the steps here and tried again but get the same result. Both the admin and myself get this issue on different devices.

It seems possible our account has been hacked as one of our passwords (not for the admin account) was found in a data breach 10 days ago. I finally have a support ticket open but have no idea when I will get a response.

I think something is wrong with our account on the backend that only Microsoft can fix.