While researching on Unity-related problems, I've observed several users getting an issue where - after logging in - they don't see anything on desktop (no sidebar, top bar ... nothing), just the wallpaper. Worse, pressing Alt+Ctrl+T doesn't bring up the terminal window as well.
Gladly, I also found a couple of solutions to this problem, which I'll be sharing with you all here. The aim is to help those who unsuccessfully faced this problem in the past or are currently struggling with this issue. Of course, there's no harm gaining this knowledge if you haven't encountered such a situation yet.
So, coming to solution-1, which is to turn the Unity plugin back on. The steps mentioned in the following screenshot explain how you can do that:
If the aforementioned instructions don't work, then here's the second solution:
Launch a tty terminal by pressing ctrl + alt + f1. Once in that terminal, run the following set of commands in the same order as listed here:
sudo rm -rf ~/.cache/compizconfig-1 sudo rm -rf ~/.compiz sudo rm -rf ~/.Xauthority sudo dconf reset -f /org/compiz/ setsid unity sudo reboot
If the first solution didn't work, then this one should definitely work. In case you used a different solution to resolve such an issue, share that with us in comments below.