Error with flashing Jetpack 4.6.2 on Jetson AGX

I am receiving the following error when I am trying to setup my Nvidia Xavier AGX. I am using host machine with Ubuntus18.04
I cannot flash Nvidia Xavier AGX. below you can find the error that I am receiving on sdkm.

SDK Manager is verifying system readiness to install.
Access to APT repository and ability to install Debian packages with it.
Your system is not ready for install, see specific errors below. Once fixed, click ‘Retry’ to verify system readiness again.
Access to APT repository and ability to install Debian packages with it.: Apt repository check failure (sudo -S apt-get update && sudo -S apt-get check).
404 Not Found [IP: 91.189.91.39 80]

hello a.elhanashi,

that’s failed by accessing to APT repository,
please execute apt-get update on your host machine for confirmation.

please examine your /etc/apt/sources.list.
if you still see the 404 failure, you may modify the file to leave only http://<region>.archive.ubuntu.com/ubuntu/ xxx in the sources list.