Windows Sandbox fails to open with 0x800705B4

Error in Windows Sandbox, Windows version win11 25h2 26200.7462 error (0x800705B4) timeout

I have tried uninstalling and installing the Windows Sandbox feature and I get the same error.

I have tried deleting the registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Containers\CmService

then uninstalling Windows Sandbox, restarting, and then reinstalling to regenerate all the files, and the result is the same error.

The problem or bug lies in the fact that when Windows Sandbox runs, in the directory C:\ProgramData\Microsoft\Windows\Containers\ContainerStorages, a folder is generated containing files created by the executable WindowsSandboxServer.exe, specifically sandbox.vhdx and .vmgs.

Generally, these files don't usually occupy more than 200 megabytes, but since the Windows 11 December system update was installed, the files being generated can reach more than 1 gigabyte.

When they reach that size, the WindowsSandboxServer.exe process shuts down automatically, I assume due to some kind of bug or timeout the files that were being generated (which are the base of the Windows Sandbox) disappear due to the aforementioned bug or process timeout,

and that is when the WindowsSandboxRemoteSession process shows you the error:

Could not initialize Windows Sandbox.

This operation returned because the timeout period expired. (0x800705B4)

It is clear that this is a bug. I should mention that the Windows Sandbox application is updated from the Microsoft Store.

Best regards,

Hello,

Your symptom matches a known change in Windows 11 where, starting with version 24H2, the in-box Windows Sandbox hands off to a newer Windows Sandbox app delivered through Microsoft Store. If the Store cannot be reached or the update is still pending, launch can sit at the logo and then time out with 0x800705B4.

Do this to get it working again.

Open Microsoft Store, go to Library, select Get updates, and let the Windows Sandbox app update install completely. If you do not see it in Library, search Microsoft Store for Windows Sandbox and choose Update or Install. Keep the Store open until it finishes, then launch Windows Sandbox again. If your network or policy blocks Store access, connect to a network that allows Microsoft Store and repeat the same steps.

If that does not resolve it, tell me and I will guide you through the next step.

Still not working on Windows 11 build 26200.7462.

I have exactly the same problem on 20 machines please fix this ASAP ( i tried everything, in my case nothing worked) .

Thanks