"Manifest validation failed" in M365 Admin Center

Hi Zahmedli

I understand how confusing this can be, especially when the manifest passes local validation but fails during deployment. 

This may occur because validation in the Microsoft 365 Admin Center goes beyond what the local office-addin-manifest validate tool checks. While the local tool focuses on validating the manifest structure and format, the Admin Center may also verify whether certain values, particularly in the WebApplicationInfo section, are consistent with your app registration in Microsoft Entra ID. 

With recent updates aligned to the Unified App Model, these additional checks may be more strictly enforced, which can lead to cases where a manifest passes local validation but is rejected during deployment. 

I recommend reviewing the following points: 

-Ensure the Id matches a valid App Registration client ID in your tenant

-Verify the Resource matches the Application ID URI configured for that app

-Confirm any scopes referenced are properly defined and exposed

-Check that the configuration is fully consistent and does not contain partial or mismatched values

In similar scenarios, mismatches between domains defined in the manifest and those configured in the app registration, especially when SSO is involved, may also cause this type of validation failure. 

Reference: Manifest rejected as invalid after adding WebApplicationInfo (SSO) – passes npm validation, fails i… 

As I do not have access to a test environment and want to avoid providing any potentially misleading guidance. If the issue continues after verifying the configuration, I recommend opening a new thread on the GitHub, where experienced engineers and contributors can provide more targeted assistance.

Reference: Participating in a discussion - GitHub Docs. 

I hope this helps. 

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The production validation in the Microsoft 365 Admin Center runs a newer and stricter manifest validation pipeline than the local office-addin-manifest tool. When a manifest passes locally but fails with “Manifest validation failed” in the Admin Center, the issue is typically with schema or store-level rules that the local validator does not yet enforce.

Use the following approach, focusing on the unified manifest and webApplicationInfo:

1. Re‑validate with production-level rules
   • If the project was created with Microsoft 365 Agents Toolkit or the Yeoman generator, run the production validation command from the project root:

          npm run validate -- -p
     

   • If that fails or is not available, run:

          npx office-addin-manifest validate -p MANIFEST_FILE
     

   • The -p / -- -p option applies Microsoft 365 and Copilot store–level checks that are closer to what the Admin Center uses and may surface issues that the basic office-addin-manifest validate did not report.
2. Validate the manifest file directly
   • Ensure the validation is run in the folder that actually contains the manifest being uploaded to the Admin Center, not a different or older copy.
   • If the manifest was not created with the current toolchain, also run the standalone validator explicitly on that file:

          office-addin-manifest validate MANIFEST_FILE
     

     or, if needed:

          npx office-addin-manifest validate MANIFEST_FILE
     

3. Check for schema drift and new elements
   • If using an add‑in only XML manifest and newer features (for example, <Runtimes> or other recent elements), Visual Studio or older tooling may still be using outdated XSD schemas. Update the XSDs from the latest schemas so that local design-time validation matches the current platform expectations. This helps catch structural issues before upload.
   • For Visual Studio projects, open the manifest, use the XML Document → Schemas property to locate the XSD files in use, and replace them with the latest versions from the Office XML schema reference. Then restart Visual Studio and re-check the manifest.
4. Re-check IDs, resources, and limits Even if the error appears tied to webApplicationInfo, Admin Center validation can fail for other manifest issues that local checks may miss:
   • Confirm the Id/ID is stable and not changed in the deployed copy without first removing the old add-in from tenants.
   • Ensure all resid values used in the manifest are defined in <Resources> and are ≤ 32 characters.
   • If the manifest has grown significantly (for example, many redirect URIs or permissions), verify that the total number of collection entries in the app manifest is within platform limits. Exceeding manifest limits can cause upload/update failures.
5. If using Outlook contextual activation or classic Outlook features
   • If the add-in relies on activation rules and is being migrated to or used with the unified app manifest, be aware that some activation-rule–based features are not supported with the unified manifest. In such cases, the Admin Center may reject combinations that are technically valid XML/JSON but unsupported by the platform.
6. Retry upload after corrections
   • After addressing any issues surfaced by validate -p and schema updates, regenerate the package if applicable and retry the update in the M365 Admin Center.

If the Admin Center still reports only a generic “Manifest validation failed” with no additional detail and validate -p passes, collect the exact manifest being uploaded and open a support ticket, as this can indicate a gap between the current store validator and the public tooling.

References:

• Validate an Office Add-in's manifest
• Troubleshoot development errors with Office Add-ins
• Office Add-ins manifest
• Microsoft Entra app manifest (Azure AD Graph format)
• Troubleshoot Outlook contextual add-in activation