"Files" File manager is not working on Ubuntu 20.04

"Files" File manager is not working on my Ubuntu 20.04 system.

If I try to open it from terminal by using nautilus command, still nothing is happening.

But if I try with sudo nautilus command then It can open. But each time I dont want to open it through terminal command. I want it to open through UI only as it was working before.

I had recently installed docker on my system. I thought this was happening because of docker installation. so I completely uninstalled docker using this steps. https://askubuntu.com/a/1021506/1503528 but still issue has not solved.

I have also tried below solutions. But nothing has worked for me.

1. reinstalling nautilus-data using below command (https://askubuntu.com/a/770192/1503528)

sudo apt-get install --reinstall nautilus-data

2. terminating the running nautilus process and restarting it using below commands (https://askubuntu.com/a/875311/1503528)

ps awx | grep nautilus
sudo kill -TERM <id>

3. Uninstalling and reinstalling Nautilus ( https://askubuntu.com/a/876810/1503528)

sudo apt-get remove nautilus

sudo apt-get autoremove
sudo apt-get clean
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install nautilus

Question

The issue was I had changed ownership of nautilus to root user only while doing something. Because of that I was not able to start nautilus from terminal OR "Files" from UI as a my regular USER.

Thanks to @guiverc. His Comment helped me to understand what exactly was happened.

Solution:

1. I started nautilus through sudo nautilus command.
2. In home directory right click and selected Properties.
3. In permissions tab changed user to my USER. Now I can open "Files" as it was working before.

Thanks again @guiverc