Microsoft Exchange Error

Question

When trying to add a member to a Microsoft 365 group I get the error Response Content is Null

Answer 1

Hi @Kretschmann, Kathryn G

Thank you for sharing your concerns. 

To ensure I fully understand your situation and provide the most effective assistance, I’ll need a few additional details, such as:  

Does this issue occur with one specific group or multiple groups? 

Are you able to add other users successfully to the same group? 

If possible, could you share a screenshot of the error from your side? 

Please make sure to remove or mask any sensitive or confidential information before sharing. As this is a public forum, I recommend sending the screenshot via private message instead. I have already reached out to you through private message in this thread, please check and reply there with the link using the same account. 

In the meantime, you could try performing the action using an InPrivate/Incognito browser session to rule out any browser-related issues. 

Any update would be appreciated.

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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Answer 2

The error “Response Content is Null” when adding a member to a Microsoft 365 group typically indicates that the underlying add-member operation failed and returned no usable payload. From the provided context, the most relevant supported cause is when the target group cannot be managed by the API or method being used.

When adding members via Microsoft Graph or tools that rely on it, the operation fails with a 403/empty response if the group type is unsupported. Microsoft Graph supports only Microsoft 365 groups and security groups. If the group is a different type (for example, a mail-enabled security group not supported in that path, or another non–Microsoft 365 group type), the add-member call cannot be completed and may surface as a generic or null-content error in the client.

To troubleshoot within the supported guidance:

1. Verify the group type
   • Confirm that the target object is a Microsoft 365 group (Unified group) or a security group.
   • If it is not one of these supported types, create or use a Microsoft 365 group or security group instead and add the member there.
2. If using Microsoft Graph or a Graph-based tool
   • Ensure the group is a Microsoft 365 or security group.
   • If the group is of a supported type and the error persists, check that the account performing the operation has sufficient permissions to manage group membership.
3. If the member is a guest user and the add fails
   • If adding a guest to a Microsoft 365 group fails with a generic error, check whether that guest already exists as a user object in Microsoft Entra ID. If so, follow one of the documented workarounds (for example, removing or relocating the on-premises user object so the guest can be added correctly).

If the group is confirmed to be a Microsoft 365 group and the member is valid, but the client still reports “Response Content is Null,” use Exchange admin tools or the Microsoft 365 admin center to add the member directly to the group as a test. If that succeeds, the issue is likely with the specific client or API wrapper surfacing the null response rather than with Exchange Online itself.

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References:

• Troubleshoot 403 error when adding a user to a group by using Microsoft Graph API
• Problem adding one or more people to the group when you add an external contact as a guest in Microsoft 365
• Add members