Error 500121 - External Users

Question

I have had multiple problems with this error code - 500121 - where it's an external/guest user trying to access our tenants SharePoint / OneDrive that they have been invited to or had it shared with them.

Any ideas how to resolve this please? All eternal users are reporting that their MFA works perfectly well for their own tenant.

Answer 1

Hi Rebecca,

We appreciate you spent time doing tests and sharing the result with us. We understand this problem has affected your work and apologize for the inconvenience.

Considering all your external users can use account with MFA perfectly well for their own tenant and the error message only appears when they try to access SharePoint and OneDrive in your tenant, the best way to troubleshoot this issue is to report it to the related team and check your tenant from back end for further investigation.

We sincerely recommend you inform your Microsoft 365 administrator of this issue and help you create a support ticket via Microsoft 365 admin center. The support team has higher permission to remotely help you, check your tenant from background, they also have more resource to investigate the issue further. This is the most efficient way in handling this case for you.

For reference: How do I find my Microsoft 365 admin    Get support | Microsoft Docs

Thanks for your patience and understanding. Hope you are keeping safe and well!

Best regards,

Tina

Answer 2

Hi,

Thanks for the suggestion but the issue is still occurring.

I do not know if this occurs for all guests (presumably not as we have so many of them)

I believe this is happening for new guests who have recently been invited to join?

Thanks!

Answer 3

Hi Rebecca,

Good day to you. Thanks for querying in this forum.

According to your description, It seems like the error 500121 appears when an external tries to sign in with MFA to access your SharePoint or OneDrive files. Sorry for the inconvenience, we understand this issue has affected your daily work.

Based on our search for the error 500121, other users who had this error mentioned they can sign in account if they tries steps below. You may let one of your affected external user have a try and check the outcome.

Enter username and password.

When it says "More information required", don't press next.

Press "Use a different account".

Then choose the same account again to sign in.

If the error message still appears, we do understand the frustration and feel very sorry about it. Could you confirm information below? It will help us better understand the situation and do further troubleshooting:

1.Do all external users have this issue?

2.Could you share a screenshot about the error message?

3.Can they access your SharePoint site in previous? When does the issue start to happen?

Many thanks for your patience and effort. Hope you are keeping safe and well.

Best regards,

Tina