Upgrade ubuntu 14.04 to 16.04

[Juan Manuel Carrillo Campos]

When the "full upgrade of the distribution"(Actualizacion completa de la distribucion) window came to the second step "configuring new channels of software"(configurando nuevos canales de software), one of the steps shows the message "calculating the changes" (calculando los cambios), it shows a new window with a message "it has nor been able to calculate the update"(No ha sido posible calcular la actualizacion) with just the option "close"(cerrar) and the process stops after "restoring the original status of the system" step.
(in the "configuration" options, in the "Other software" section, nothing is selected)
how may I debug and fix this situation?

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.10
ProcVersionSignature: Ubuntu 3.13.0-147.196-generic 3.13.11-ckt39
Uname: Linux 3.13.0-147-generic i686
NonfreeKernelModules: wl
ApportVersion: 2.14.1-0ubuntu3.28
Architecture: i386
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Mon May 21 18:58:38 2018
InstallationDate: Installed on 2016-02-09 (832 days ago)
InstallationMedia: Ubuntu 12.04.5 LTS "Precise Pangolin" - Release i386 (20140807.1)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2018-05-21 (0 days ago)
VarLogDistupgradeTermlog: