Updater says 'check your network connection." Don’t need any help, just didn’t know where to report it. I am assuming it is a server problem.
It would be better to troubleshoot it here if you are willing.
Can you post the output of
sudo apt update
For software updater, is your server source set to “Main Server” ?
Usually this issue is caused by a user added repo that is giving a 404 error. Removing that repo by
sudo add-apt-repository -remove (PPA)
Or GUI from Software & Updates, “Other software” tab, clicking the repo, then clicking the button for “Remove”.
Then running the updater, again.
Which is why I asked the OP to run ‘sudo apt update’ to inspect the repos they have in sources.list.