The next method to solve the problem "Failed to open a session for the virtual machine" in VirtualBox, is to uninstall and then to reinstall the VirtualBox application, especially if the problem appeared after a Windows Update.
The next method to solve the problem "Failed to open a session for the virtual machine" in VirtualBox, is to uninstall and then to reinstall the VirtualBox application, especially if the problem appeared after a Windows Update.