Guest users on shared channels

Question

Hello

Please i need your help on this issue.

we are issue with Guest users on shared channels.

I have a shared file in my organization that I'd like to invite a guest user to.

I sent them the link, and even changed in my Entra center that guests have access to everything like members. I created guest user accounts. But still they are unable to access the file.

 I get this error when they try to access:

Selected user account does not exist in tenant 'Microsoft Services' and cannot access the application '243c63a3-247d-41c5-9d83-7788c43f1c43' in that tenant. The account needs to be added as an external user in the tenant first. Please use a different account.

Answer 1

@James James

Below are some troubleshooting steps and considerations to help resolve the guest access issue:

1. Verify the Guest Account Is Properly Provisioned

• Confirm that the guest user has been successfully added via the invitation process to your Azure AD (now known as Entra ID). You should see the guest account in your directory (Users → All Users).

• Ensure the guest user has redeemed the invitation email. Until they accept the invite, the account won’t be fully provisioned for access.

2. Check the Account Used for Sign-In

• Often the error “Selected user account does not exist…” happens because the guest is signing in with a different account than the one that was invited. Ask the guest to verify that they are using the same email address (or alternate sign-in address) as the one you added as a guest.

• If the guest has multiple accounts (for example, a personal Microsoft account and a work/school account), they should sign in with the guest account you provisioned in your tenant.

3. Validate External Sharing Settings

• In your Microsoft 365 admin center (and specifically for SharePoint or OneDrive, if that’s where the file is stored), confirm that external sharing is enabled. Sometimes external sharing settings might not be as permissive as what you set in Entra.

• Make sure that the file’s sharing permissions include guest access (not just being shared with internal users).

4. Review the Application’s Multi-Tenant Configuration

• The error message references an application (ID: 243c63a3-247d-41c5-9d83-7788c43f1c43). Verify which application this is (for example, it could be related to OneDrive, SharePoint, or another custom/shared app portal). Then check if its configuration allows for multi-tenant access or if there are any conditional access policies impacting external access.

• Sometimes legacy multi-tenant settings or app registrations might restrict guest access even when the user is in the guest portion of your tenant.

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