Hi Saidur,
I am Sumit, an Independent Advisor here to assist you.
Does the machine pass all the prerequisites?
https://docs.microsoft.com/en-us/windows/securi...
Prerequisites
Windows 10 Pro, Enterprise or Education build 18305 or later (Windows Sandbox is currently not supported on Home SKUs)
AMD64 architecture
Virtualization capabilities enabled in BIOS
At least 4 GB of RAM (8 GB recommended)
At least 1 GB of free disk space (SSD recommended)
At least two CPU cores (four cores with hyperthreading recommended)
Right-clcik Start>Windows Powershell(admin).
Execute the following to enable Sandbox.
Enable-WindowsOptionalFeature -FeatureName "Containers-DisposableClientVM" -All -Online.