I am trying to upgrade to LTS 16.04 and not having any luck. I am following this guide on Ask Ubuntu: How to upgrade my Ubuntu 15.04 to Ubuntu 16.04
mblanco@mblanco-MS-7680:~$ sudo do-release-upgrade
[sudo] password for mblanco:
Checking for a new Ubuntu release
No new release found
I think it might have to be associated with the sources I use for updates which are Canonical Partner, but I am not sure.