Bsrgvty

I've almost done all suggestions here, but none of them didn't work.
Also gd3 reconfigure has no effect.
But I had suspected to my last gnome extensions.

The system-monitor@paradoxxx.zero.gmail.com was the problem.
So I disabled all gnome extensions to solve login loop as following steps:

1. Press Ctrl+Alt+F2 or Ctrl+Alt+F3 or ...


2. Enter your username and password


3. cd ~/.local/share/gnome-shell/


4. mv extensions extensions.bak


5. mkdir extensions


6. Press Ctrl+Alt+F1
   


7. Login and Thanks God

Hope help somebody else. I almost worked full day to find this solution.

PS: I've installed my favorite extentions again and I have to tell you Login Loop disaster in ubuntu has wide variety causes. So try to find your special cause and solve it.

Looks like it may have been related to "upgrading" from 18.04 to 18.04.01: No login screen after ubuntu 18.04.1 update

In any case, doing the following fixed it for me:

systemctl stop gdm.service 
systemctl restart gdm.service 
sudo dpkg-reconfigure gdm3 
reboot

I also had tried a lot of solution but none of that work for me, but this did.

1. Press Ctrl+Alt+F2
   


2. Login with your username and password


3. Enter ls -ld ~/ after you will see something like this
   drwxr-xr-x 30 root root 4096 Jul 6 20:26 /home/yourcutename/

   


4. Now Enter sudo chown username:username /home/yourcutename/
   

This worked for me :-)

My ubuntu loop login problem started after switching from java11 openjdk to java8 openjdk.
I had logged in via CTRL+ALT+F3 to terminal and switched back to java 11 via
sudo update-alternatives --config java and login loop stopped.

i have that same problem on Ubuntu 19.04. What i did was reinstall gnome and works fines.

sudo apt-get install gnome-session gnome

Then on the log in screen i change to gnome

My issue started after I messed with the /etc/environment file by adding the following to my path variable:

PATH=$JAVA_HOME:$PATH

I fixed the issue by going into one of the strips down mode in grep, launching a command prompt, launching VI and removing the above.

I believe what happens, is by messing with the path variable, Ubuntu couldn't find some things.

I initially did this because I installed java manually.

I faced the same problem with my Ubuntu 18.04 a couple of days ago. I tried all the mentioned solutions on the web. But I think, in the end, the problem with mine was some wonky graphics drivers. All I did was log in on my system on Ubuntu Wayland (by clicking that gear button at the time of login) opened the Terminal Window and upgraded. The commands were:

 sudo apt update
 sudo apt upgrade

And then rebooted my system. Ready as new!!!
If you want you can stay and use it on Wayland, but some applications do not work properly on Wayland (like VLC).

Well, the other solutions on the web did not work for me. So, all the others and even if this solution does not work then I think only one option is left: Reinstall

The cause for me was that I was playing around with the DISPLAY variable
and had set export DISPLAY=:1.0 in my .profile

when I commented out that line, I could log in again ie. no more looping.

This issue seems to have a different solution for everyone. I tried many different solutions that I found throughout forums and nothing worked for me. After looking around I found the issue was that somehow my user had lost write permissions in my own $HOME folder.... Solution for me was:

1. Load command line (ALT+CTRL+F2 or ALT+CTRL+F3)


2. chmod 755 $HOME


3. restart the Desktop Environment.

Hope this can help someone else.