Comment # 16 on bug 1203540 from Jonathan Kang

Are you able to see the authentication dialog when you are installing/removing
a package using pkcon, for example "pkcon install eog"?

I'm assuming polkit-gnome wasn't able to pop up the authentication dialog
somehow. To further debug this, change 
> Exec=/usr/lib/polkit-1/polkitd --no-debug
in /usr/share/dbus-1/system-services/org.freedesktop.PolicyKit1.service to
> Exec=/bin/sh -c 'G_MESSAGES_DEBUG=all /usr/lib/polkit-1/polkitd > /tmp/polkit-gnome.log 2>&1"
restart the system if possible, reproduce this and check the content in
/tmp/polkit-gnome.log.