The update from Ubuntu 14.04 to 16.04 doesnt work

[Tom]

Upgrading form Ubuntu 14.04 to 16.04: Error message

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

 This can be caused by:
 * Upgrading to a pre-release version of Ubuntu
 * Running the current pre-release version of Ubuntu
 * Unofficial software packages not provided by Ubuntu

If none of this applies, then please report this bug using the command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.9
ProcVersionSignature: Ubuntu 4.4.0-109.132~14.04.1-generic 4.4.98
Uname: Linux 4.4.0-109-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.27
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Thu Jan 11 20:42:31 2018
InstallationDate: Installed on 2015-11-06 (797 days ago)
InstallationMedia: Ubuntu 14.04.3 LTS "Trusty Tahr" - Beta amd64 (20150805)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2018-01-11 (0 days ago)
VarLogDistupgradeTermlog: