unable to upgrade from 18.04 to 20.04

[Austin]

when attempting to upgrade from 18.04 to 20.04 i get:

Calculating the changes

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

This was likely caused by:
* Unofficial software packages not provided by Ubuntu
Please use the tool 'ppa-purge' from the ppa-purge
package to remove software from a Launchpad PPA and
try the upgrade again.

If none of this applies, then please report this bug using the
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. If
you want to investigate this yourself the log files in
'/var/log/dist-upgrade' will contain details about the upgrade.
Specifically, look at 'main.log' and 'apt.log'.

I have tried using ppa-purge, but this did not make a difference

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.40
ProcVersionSignature: Ubuntu 5.4.0-54.60~18.04.1-generic 5.4.65
Uname: Linux 5.4.0-54-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.20
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Wed Nov 25 17:10:19 2020
InstallationDate: Installed on 2020-10-12 (44 days ago)
InstallationMedia: Ubuntu 18.04.5 LTS "Bionic Beaver" - Release amd64 (20200806.1)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-11-25 (0 days ago)