Massive trouble with upgrade of 16.04

[Shawn_Hawkins]

I did a fresh install of ubuntu 16.04 and created a live usb install of 18.04 to upgrade the system. I had no errors or warnings or issues with the install or making the usb or with the software upgrade. But now, when i hit F12 to boot from usb the boot screen doesnt show up, i just get a blank, black screen. So i restarted in order to hit F2 to go into the setup menu but it is blank as well.
Can anyone figure out what is wrong? Ubuntu runs fine so far, i just can't boot into usb or adjust the startup.
I have a dell e6420, 6 Gig of ram, 1 terabyte hard drive running ubuntu 16.04
I need help. I dont know what to do. I just checked and it only shows a blank screen when the usb is plugged in.

[Autodave]

In my own experiences over the years, upgrading rarely works. (Others will disagree with that.) Why not just do a clean install of 18.04?

[oldos2er]

Is your computer UEFI or MBR? If UEFI, do you have Secure Boot enabled? Try disabling it first.