The Windows Sandbox is a "lightweight virtual environment" and one of the biggest highlights of the Windows 10 1903 update. However, many users are now experiencing problems here. When they try to start it, it always displays an error message, which makes it unusable.
Windows Sandbox may fail to start with "ERROR_FILE_NOT_FOUND (0x80070002)" on devices in which the operating system language is Changed during the update process when installing Windows 10, version 1903.
FromMicrosoftThe support team's technicians have stated that the issue affects devices that have changed their operating system language during the Windows Update installation. Today, Microsoft updated its documentation to confirm that it is addressing the issue and estimated that a fix "will be available at the end of August."
It's worth noting that Microsoft just released Windows 10 Build 18362.325 to Windows Insiders in the release preview channel, and fixed the Sandbox issue in this release.
If Windows 10 Build 18362.325 is finally confirmed by Microsoft, it will be sent to all users within a few days, and the Sandbox issue will eventually be fixed.