vtoy in eufi problem

[Steve2926]

Supported vDisk Format
Fixed size vhd (vhdx is not supported)
Fixed size vdi
Raw Disk Image


So are you using a FIXED SIZE VHD or VDI?
https://ventoy.net/en/plugin_vtoyboot.html
In order to make the vhd/vdi file bootable in both Legacy BIOS mode and UEFI mode.
You must set VirtualBox to UEFI mode before install OS !!!

You will need to be more precise on exactly what you are doing.
https://youtu.be/uBjpJl5nMGQ