This is the current version I have
lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.5 LTS
Release: 16.04
Codename: xenial
When I try
sudo do-release-upgrade
Error during update
A problem occurred during the update. This is usually some sort of
network problem, please check your network connection and retry.
Restoring original system state
Aborting
Reading package lists... Done
Building dependency tree
Reading state information... Done
If I try
ThinkPad-T520:~$ sudo apt-get upgrade
[sudo] password for usernameXYZ:
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
-ThinkPad-T520:~$ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 16.04.5 LTS Release: 16.04 Codename: xenial