Hi PavolKindernay,
Welcome to the Microsoft Community.
It sounds like you are encountering the "Windows Sandbox failed to initialize" error on your Windows 10. Sorry to hear this.
While this issue is beyond the scope of support of this Community Forum and is facing developers since it's related to Windows Sandbox and Hyper-V. And for further investigations, this issue is more suitable to be published in windows-10-hyperv - Microsoft Q&A. This community caters to IT professionals who can provide advanced troubleshooting steps for your concern. And you can click on Ask a Question to start.
Do get back to us if there is any problem in future use. We'll be glad to assist.
Best regards
| Lynn Sun Microsoft Community Support Specialist
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