In an environment where user synchronization is done with an alternate ID, SSO for M365 apps is not working well

Question

After I connect to an AVD session host [Windows 11 Enterprise multi-session (including M365)],

I starting M365 desktop applications (Excel, Word, PowerPoint, Teams).However SSO does not occur.

Could you please provide the cause and solution?

■Verified Details

・M365 application version: Latest.

・Computer object [AzureADSSOAcc] in on-premise AD: Created.

・SSO confirmation in browser (Google Chrome):

　- Normal mode　: SSO works

　- Incognito mode: Not SSO

・Microsoft's official documentation Settings: ALL Configured

　URL: https://learn.microsoft.com/ja-jp/entra/identity/hybrid/connect/how-to-connect-sso-quick-start

・Security Log　: There are no logs containing "AzureADSSOAcc$"

・Other things : After some time upon starting Excel, I Run Klist command ,It is cached "[http://autologon.microsoftazuread-sso.com]: <on-premise AD domain name>.LOCAL".

※Note: "AzureADSSOAcc$" is not cached.

■Configuration

<Microsoft Entra ID Connect>

・SSO enabled (confirmed on Entra ID).

・Password hash synchronization.

・User synchronization with alternate ID (ST attribute is synchronized as UPN).

※Note: The UPN for on-premise AD and Entra ID differs.

<ADFS>

・Not configured.

Answer 1

Hello @熊谷 吉斗,

Based on your query, I understand you want to set up SSO for all M365 Apps.

SSO will work on a normal browser when you open any M365 Apps, but it will not work in the In-private window on any browser (Chrome, Edge) because Azure AD Seamless SSO does not work in private/incognito mode. This is because browsers block automatic authentication (Kerberos/NTLM) and do not retain session cookies. Additionally, it won’t work in Internet Explorer's Enhanced Protected Mode or when Enhanced Security Configuration is enabled.

Here the Reference Doc:

https://learn.microsoft.com/en-us/entra/identity/hybrid/connect/tshoot-connect-sso

I hope this information is helpful. Please feel free to reach out if you have any further questions.

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