update issue

[Dankmark]

Hello, I use this:
apt update, sudo apt-get update
but couldn't update my linux 20.04.4 LTS yet I was able to upgrade it
this error came by:

root@eve-ng:~# sudo apt-get update
Get:1 http://lv.archive.ubuntu.com/ubuntu focal InRelease
Err:1 http://lv.archive.ubuntu.com/ubuntu focal InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:2 http://lv.archive.ubuntu.com/ubuntu focal-updates InRelease
Err:2 http://lv.archive.ubuntu.com/ubuntu focal-updates InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:3 http://lv.archive.ubuntu.com/ubuntu focal-backports InRelease
Err:3 http://lv.archive.ubuntu.com/ubuntu focal-backports InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:4 http://lv.archive.ubuntu.com/ubuntu focal-security InRelease
Err:4 http://lv.archive.ubuntu.com/ubuntu focal-security InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Hit:5 http://www.eve-ng.net/focal focal InRelease
Reading package lists... Done
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository 'http://lv.archive.ubuntu.com/ubuntu focal InRelease' is not signed.
E: Failed to fetch http://lv.archive.ubuntu.com/ubuntu/dis ... /InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository 'http://lv.archive.ubuntu.com/ubuntu focal-updates InRelease' is not signed.
E: Failed to fetch http://lv.archive.ubuntu.com/ubuntu/dis ... /InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch http://lv.archive.ubuntu.com/ubuntu/dis ... /InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository 'http://lv.archive.ubuntu.com/ubuntu focal-backports InRelease' is not signed.
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: Failed to fetch http://lv.archive.ubuntu.com/ubuntu/dis ... /InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository 'http://lv.archive.ubuntu.com/ubuntu focal-security InRelease' is not signed.
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.
...
How to fix this issue?
Best Regards

[Uldis (UD)]

It looks like DNS issue, re-check your server Ubuntu network settings