I tried all the mentioned solutions and none worked for me! here is the output of sudo appstreamcli refresh --force --verbose:

** (appstreamcli:5211): DEBUG: Refreshing AppStream cache
** (appstreamcli:5211): DEBUG: Reading: /usr/share/app-info/xmls/org.freedesktop.fwupd.xml
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/security.ubuntu.com_ubuntu_dists_xenial-security_main_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/security.ubuntu.com_ubuntu_dists_xenial-security_restricted_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/ca.archive.ubuntu.com_ubuntu_dists_xenial_main_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/ca.archive.ubuntu.com_ubuntu_dists_xenial_restricted_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/ca.archive.ubuntu.com_ubuntu_dists_xenial_universe_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/ca.archive.ubuntu.com_ubuntu_dists_xenial_multiverse_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/ca.archive.ubuntu.com_ubuntu_dists_xenial-updates_main_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/ca.archive.ubuntu.com_ubuntu_dists_xenial-updates_restricted_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/ca.archive.ubuntu.com_ubuntu_dists_xenial-updates_universe_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/ca.archive.ubuntu.com_ubuntu_dists_xenial-updates_multiverse_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/ca.archive.ubuntu.com_ubuntu_dists_xenial-backports_main_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/ca.archive.ubuntu.com_ubuntu_dists_xenial-backports_restricted_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/ca.archive.ubuntu.com_ubuntu_dists_xenial-backports_universe_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/ca.archive.ubuntu.com_ubuntu_dists_xenial-backports_multiverse_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/security.ubuntu.com_ubuntu_dists_xenial-security_universe_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: Reading: /var/lib/app-info/yaml/security.ubuntu.com_ubuntu_dists_xenial-security_multiverse_dep11_Components-amd64.yml.gz
** (appstreamcli:5211): DEBUG: No metadata-specific subdirectories found in '/var/cache/app-info'
** (appstreamcli:5211): DEBUG: Detected colliding ids: eog.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-base.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: thunderbird.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-impress.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: display-im6.q16.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: firefox.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-calc.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-startcenter.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-math.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-draw.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: display-im6.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-writer.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: plan.desktop was already added with the same priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: flcheckers.desktop was already added with the same priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: flblocks.desktop was already added with the same priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: flsudoku.desktop was already added with the same priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-startcenter.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'org.gnome.Calendar.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-base.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'gnome-session-properties.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-math.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'software-properties-gtk.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'software-properties-gnome.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'software-properties-drivers.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'org.gnome.font-viewer.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'org.gnome.Nautilus.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'gnome-sudoku.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-draw.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'language-selector.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'org.gnome.FileRoller.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'org.gnome.Software.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: eog.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'gnome-system-monitor.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'gnome-system-monitor-kde.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'ubiquity.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-impress.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-writer.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: firefox.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: display-im6.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'upstart-monitor.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'vim.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: thunderbird.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: display-im6.q16.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'xdiagnose.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'gvim.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'vino-preferences.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Detected colliding ids: libreoffice-calc.desktop was already added with a higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'unity-keyboard-panel.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'unity-region-panel.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'unity-network-panel.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'unity-sound-panel.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'unity-datetime-panel.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'unity-universal-access-panel.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'unity-mouse-panel.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'unity-wacom-panel.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'unity-user-accounts-panel.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'unity-appearance-panel.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'unity-bluetooth-panel.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'unity-color-panel.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'nm-connection-editor.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'evolution-bogofilter' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'evolution-spamassassin' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'mplayer.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'virt-manager.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'ubuntu-mate-welcome.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'ubuntu-mate-software.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'htop.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'light-locker-settings.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'org.gnome.Documents.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'org.gnome.Books.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'owncloud.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'evolution.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'org.gnome.Maps.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'CMake.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'gufw.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'ccsm.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'abiword.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'org.gnome.Contacts.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'lshw-gtk.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'org.gnome.taquin.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'ubiquity-kdeui.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'chromium-browser.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'boinc-manager.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'virtualbox.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: Replaced 'chromium-browser.desktop' with data of higher priority.
** (appstreamcli:5211): DEBUG: zathura-pdf-poppler.desktop extends zathura.desktop, but zathura.desktop was not found.
** (appstreamcli:5211): DEBUG: Removing old rebuild-dir from previous database rebuild.
AppStream cache update completed successfully.