I got a black screen instead of login, It was really stressful, being locked out of my own hard drive/OS is just a horrible experience.
I ended up solving it. So what happened was, I was downloading a file that had 20 minutes left until finished in my internet browser. So I left the single tab internet browser open & told my terminal
"sudo shutdown +50".
Many hours later I rebooted & got a black screen, I couldnt do jack. So I hit Ctrl F5, tried to login that way, it let me log in via terminal, but couldnt launch the GUI login screen. Then i did
sudo apt install --reinstall zorin-os-desktop.
Bingo, This is all that i needed to do, it fixed it, thank goodness.
But what caused this serious glitch to occur in the 1st place? i dont know.
instead of only doing
sudo shutdown should i have maybe ran a kill all process? to help Zorin shutdown?