Can't access Ubuntu graphical user interface

Question

The problem is I can't access the Ubuntu graphical user interface.

I have two operating systems: Ubuntu and Windows 7 in the same computer. When I turn on the computer, I choose which OS I want to use.

Normaly when I choose Ubuntu, it opens normally and I can use the graphical user interface.
But today when I tried to use Ubuntu, it demands me my login and password and then it's just the terminal that is open.

This is what is shown in screen after choosing Ubuntu:

After logging in, this is shown in the screen:

I didn't have access to graphical user interface(GUI). Generally after choosing Ubuntu, this will be displayed:

Also there's short message in the screen that says that there's a new version of Ubuntu 20.4. I wonder if I should update to solve the problem. How should I solve this problem? (I'm begginer in using Linux environment.)

Answer 1

Try reinstalling gdm3:

sudo apt install --reinstall gdm3

or start gdm manually from TTY:

sudo gdm3

or install lightdm:

sudo apt install lightdm

or try to install drivers:

sudo ubuntu-drivers autoinstall

Answer 2

try the following commands:

• first: this will display the target being used

  $ systemctl get-default
  

• second, you can actually run the follwing command to switch to the graphical- target

  $ systemctl isolate graphical-target