My ubuntu is 18.04, and if I boot my computer with the press of the Tab(It just show the purple screen, then display the login screen) and it will boot normally. But if without press the Tab(This time it just black, and nothing else), my computer will always be a black screen. I can't figure out what problem is it. Can someone help me? If you need some more other information, Please let me know?
I had the same issue.
When your computer starts press
ESC key and it'll take you to the system setup settings with BIOS and everything.
Then select System Recovery ,in mine I had to press
F11 for System Recovery it might be different in yours.
You'll then be directed to the Ubuntu advanced settings screen where you can run Ubuntu in recovery mode .
After you run it in recovery , select
Update or remove broken dpkg in grub
Then you'll be get a screen with multiple options select the first option that is install new software and press y for everything.