"Update Software" not opening

[david braun]

The "Update Software" Icon showed that there were updates available (small triangle on left edge). Left clicking on icon didn't appear to do anything (no window appeared). Right clicking displayed a menu of options. Based on a previous encounter with this problem I entered

  "wmctrl -R "Software Updater"

which opened the expected window in the center of the screen.

lsb_release -rd
Description: Ubuntu 18.04 LTS
Release: 18.04

apt-cache policy update-manager
update-manager:
  Installed: 1:18.04.11.1
  Candidate: 1:18.04.11.1
  Version table:
 *** 1:18.04.11.1 500
        500 http://us.archive.ubuntu.com/ubuntu bionic-proposed/main amd64 Packages
        500 http://us.archive.ubuntu.com/ubuntu bionic-proposed/main i386 Packages
        100 /var/lib/dpkg/status
     1:18.04.11 500
        500 http://us.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
        500 http://us.archive.ubuntu.com/ubuntu bionic/main i386 Packages

I expected a dialog listing the updates available.

Nothing happened.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: update-manager 1:18.04.11.1
ProcVersionSignature: Ubuntu 4.15.0-23.25-generic 4.15.18
Uname: Linux 4.15.0-23-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
CurrentDesktop: Unity:Unity7:ubuntu
Date: Fri Jun 8 12:05:54 2018
EcryptfsInUse: Yes
GsettingsChanges:
 b'com.ubuntu.update-manager' b'show-details' b'true'
 b'com.ubuntu.update-manager' b'window-height' b'374'
 b'com.ubuntu.update-manager' b'first-run' b'false'
 b'com.ubuntu.update-manager' b'window-width' b'645'
 b'com.ubuntu.update-manager' b'launch-time' b'int64 1528455252'
HWEreplacements:

HWEunsupported: linux-image-extra-3.16.0-77-generic linux-image-3.16.0-77-generic
InstallationDate: Installed on 2015-05-31 (1103 days ago)
InstallationMedia: Ubuntu 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1)
PackageArchitecture: all
SourcePackage: update-manager
UpgradeStatus: Upgraded to bionic on 2018-05-10 (28 days ago)