Cannot upgrade Windows 10

I have a Lenovo laptop and non-UEFI installation of Windows Enterprise on it. I'm stuck on version 1803. When I try to upgrade to 1909, it downloads and installs it but after reboot no OS cannot be found until I go in to BIOS and enable legacy mode. When I then log in to Windows and open Updates, it says "we couldn't install this update, but you can try again (0x80004005)". How can I upgrade Windows?