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Teams Developer Portal: 412 Error "Sandbox Resources not available" and Validation Steps Skipping

Edgar Aguilar 25 Reputation points
2026-01-30T15:02:16.1533333+00:00

Hi,

I am experiencing a recurring issue with the Automatic App Validation tool that is preventing me from preparing my app for the Microsoft Teams Store.

The Issue: I successfully ran the validation twice earlier today. However, since the third attempt, I have been unable to run it again. Every subsequent attempt returns a 412 Precondition Failed error with the following message:

"Sandbox Resources are not available at the moment."

I experienced the same issue yesterday: after just a few "successful" attempts, every subsequent try returned the same error for the remainder of the day.

Attempted Troubleshooting:

  • Cross-Platform Failure: I tried running the validation via both the Teams Developer Portal (Web) and the Teams Toolkit for VS Code. Both return the same error.
  • Manifest Changes: I have made zero changes to the manifest or the app package between the successful runs and the failures.
  • Environment: My tenant is located in the United States region.

Observed Behavior during "Successful" runs: Even when the validation did not return a 412 error, the process skipped these steps:

  1. Upload Manifest.zip in MS Teams
  2. Install App in Team Scope

The process simply stops after skipping these, providing no feedback on whether those steps passed or failed.

Questions:

  • Why is the validation tool skipping the installation/upload steps even when it "runs"?
  • Does the "Sandbox Resources are not available" error indicate a daily usage quota or a regional capacity issue in the US?
  • How can I reset this state to ensure a full validation so I can proceed with my Store submission?

Any insights from the product team or others who have faced this "Sandbox" lockout would be greatly appreciated.

Microsoft Teams | Development
Microsoft Teams | Development
Building, integrating, or customizing apps and workflows within Microsoft Teams using developer tools and APIs
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Answer accepted by question author
  1. Teddie-D 11,675 Reputation points Microsoft External Staff Moderator
    2026-01-31T02:21:10.2633333+00:00

    Hi @Edgar Aguilar 

    Thank you for posting your question in the Microsoft Q&A forum. 

    Based on my findings, there isn’t currently any official documentation or prior discussion that directly addresses this issue. The validation tool skips the Upload and Install steps when it cannot provision a sandbox environment. When sandbox provisioning fails or only partially succeeds, the validator completes the static checks but silently skips all environment‑dependent steps. Because no hard error is triggered, the run is reported as successful even though no upload or installation validation actually occurred. 

    The “Sandbox Resources are not available” message does not indicate any daily usage quota on your side, the HTTP 412 response indicates that the preconditions for creating a sandbox environment weren’t met.  In practice, this usually happens when the shared sandbox infrastructure in a given region is temporarily saturated or unstable. When that occurs, new sandbox requests are blocked and retries will continue to fail until capacity is restored. This explains why the error can persist for hours or even the rest of the day, regardless of changes to the app or manifest.  

    Unfortunately, there is no client‑side way to reset or force the sandbox to become available. The only practical options are to wait for the regional sandbox pool to recover, often after some time or overnight. Once backend capacity is freed up, the validator will automatically resume full runs without any action required on your part. 

    I hope this information is helpful. 

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread. 

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  1. Q&A Assist
    2026-01-30T15:02:26.5733333+00:00
    AI generated content. This question contains an answer created with AI from Q&A Assist. Learn more

    The 412 Precondition Failed error with the message "Sandbox Resources are not available at the moment" typically indicates that there is an issue with the availability of the resources required for the validation process. This could be due to a temporary capacity issue in the region or a daily usage quota being reached. Here are some insights regarding your questions:

    1. Skipping Installation/Upload Steps: The validation tool may skip certain steps if it detects that the necessary resources are not available or if it cannot establish a connection to perform those actions. This behavior can be linked to the sandbox environment's current state or limitations.
    2. Regional Capacity Issue: Yes, the error could indicate a regional capacity issue, especially if you are consistently encountering this error after successful runs. It might be worth checking if there are any known outages or maintenance activities affecting the Teams Developer Portal in your region.
    3. Resetting the State: Unfortunately, there isn't a direct method to reset the sandbox state. However, you can try the following:
      • Wait for a period and attempt to run the validation again, as the issue may resolve itself once the sandbox resources are available again.
      • Check the Microsoft Teams Developer documentation or forums for any updates regarding known issues or outages.
      • If the problem persists, consider reaching out to Microsoft support for further assistance.

    In summary, the error you're facing is likely related to resource availability, and patience or support from Microsoft may be necessary to resolve it.

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