Why Ubuntu is not installing on VirtualBox?

In Virtualbox, shut down the vm, then edit settings of the Ubuntu Virtual Machine, then go to Display. Move the “Video memory” slider all the way to the right. Then also tick Acceleration: Enable 3D Acceleration. I already had ram increased, but these changes fixed the issue for me.

How do I run Ubuntu on Windows 10 on VirtualBox?

The current version of Ubuntu only works on 64-bit machines. Check the Windows Control Panel to tell if you’re running a 32-bit or 64-bit system. Open VirtualBox and select New in the top taskbar. Give your VM a name, choose Linux as the Type, then choose Ubuntu as the Version and select Next.