I messed up the GRUB loader and couldn't repair it, so I decided to format the partition and install a fresh copy KDE neon.

I installed same version of KDE neon that worked last time (kept it on a hard-drive, 5.16.something). After installing and rebooting the computer, I was presented with Grub loader and proceeded to launch the system.
The system showed me the Neon logo, then the HP logo and then nothing happened.
Computer would shutdown if power button was pressed.
All the virtual terminals (ctrl+alt+F2, F3...) were also working and I was able to login into text mode through those virtual terminals.

Things I have tried:
1. Creating image through two different tools, rufus and etcher.
2. Both ISO and DD image in rufus.
3. Installed a different distro (pop!_OS) to verify that the system was fine.
4. Deleting everything related to KDE neon, including all partitions and boot-loader every time I installed it
5. Putting GRUB-loader in a different place.

If you can get to a terminal, did you try pkcon refreash and pkcon update and then reboot. This is solved the boot to black screen for me several times.

thunder422 wrote:If you can get to a terminal, did you try pkcon refreash and pkcon update and then reboot. This is solved the boot to black screen for me several times.

I can go into virtual terminals (ctrl + alt + F2 . . .) but can't do anything in the GUI part, other than navigating into virtual terminals.

I found an old post where someone had similar problem. Someone suggested the OP download a new/different ISO and do another fresh install with the new ISO. I did it and its working fine now.

Thank you for the reply, will try it if I face another problem like this.