Ubuntu 20.04 sudo apt update The repository 'http://my.archive.ubuntu.com/ubuntu focal Release' no longer has a Release file

I using ubuntu

Description: Ubuntu 20.04.3 LTS

Release: 20.04

Codename: focal

I tried sudo apt update, previously no issue but recently I get this error as below

Ign:2 http://my.archive.ubuntu.com/ubuntu focal-updates InRelease
Ign:3 http://my.archive.ubuntu.com/ubuntu focal-backports InRelease
Ign:4 http://my.archive.ubuntu.com/ubuntu focal-security InRelease
Err:5 http://my.archive.ubuntu.com/ubuntu focal Release
  404  Not Found [IP: 202.79.184.254 80]
Err:6 http://my.archive.ubuntu.com/ubuntu focal-updates Release
  404  Not Found [IP: 202.79.184.254 80]
Err:7 http://my.archive.ubuntu.com/ubuntu focal-backports Release
  404  Not Found [IP: 202.79.184.254 80]
Err:8 http://my.archive.ubuntu.com/ubuntu focal-security Release
  404  Not Found [IP: 202.79.184.254 80]
Reading package lists... Done
E: The repository 'http://my.archive.ubuntu.com/ubuntu focal Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://my.archive.ubuntu.com/ubuntu focal-updates Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://my.archive.ubuntu.com/ubuntu focal-backports Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://my.archive.ubuntu.com/ubuntu focal-security Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

I checked the http://my.archive.ubuntu.com/ubuntu, the url is not found.

Any idea on this ? I am newbie on linux.

Thanks