why can't mount or access data on the hard drive that has vtoy as boot

[candrapersada]

why when I access the external hard there is an error message to access the data that I store on an external hard that has Linux.vhd.vtoy as boot?

[ventoy]

That's the limit of the linux kernel. Ventoy create a device-mapper block device based on the location of the vtoy file in the main partition. After that the main partition will become busy and can NOT mount.

So when you boot the vtoy file the main partition can not be mounted. if you want to access the USB key I suggest you reinstall Ventoy and reserve some space at the end of the USB key and create an extra partition with the reserve space.