How to fix Invalid virtual CPU count: 0

on vps linux ubuntu 18.04

CPU Cores 9 Total CPU Speed 19.2Ghz Memory 8Gb Disk Space 160Gb Bandwidth 8000Gb

instal virtualbox : https://tecadmin.net/install-virtualbox-on-ubuntu-18-04/

problem :

Failed to save the settings of the virtual machine windows 10 to /root/VirtualBox VMs/windows 10/windows 10.vbox.

Invalid virtual CPU count: 0 (must be in range [1, 32]).

Result Code: NS_ERROR_INVALID_ARG (0x80070057) Component: SessionMachine Interface: IMachine {5047460a-265d-4538-b23e-ddba5fb84976}