I've attached a strace of software-properties-gtk, taken with the "strace -fr -o software-properties-gtk.strace software-properties-gtk" command. The only thing which stands out to me is that there are a *lot* of EAGAIN entries for file descriptor 3, which appears to be the local "/tmp/.X11-unix/X0" socket. The file exists, and has what I'd expect to be usable ownership and permissions.
$ ls -l /tmp/.X11-unix/X0 srwxrwxrwx 1 adric adric 0 Feb 12 09:24 /tmp/.X11-unix/X0 AS PJSingh5000 indicated, the only message displayed on the terminal was ERROR:root:Authentication canceled, changes have not been saved ** Attachment added: "strace of software-properties-gtk" https://bugs.launchpad.net/ubuntu/+source/software-properties/+bug/1660100/+attachment/4817552/+files/software-properties-gtk.strace -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to software-properties in Ubuntu. https://bugs.launchpad.net/bugs/1660100 Title: Unable to enable or disable repository in Software & Updates Status in software-properties package in Ubuntu: Confirmed Bug description: The Software & Updates dialog (software-properties-gtk) does not allow the user to activate or deactivate repositories. RECREATE ISSUE: Launch Software & Updates. Select Other Sources tab. Click on a check box next to a repository to enable or disable it. RESULT: The window seems to lose focus, but noting happens. EXPECTED RESULT: A dialog should appear prompting the user to enter the administrator password. After the password is successfully entered, the repository check box should be toggled (enabled or disabled). OTHER DETAILS: This issue was tested on Ubuntu-Gnome. $ lsb_release --all No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 16.10 Release: 16.10 Codename: yakkety $ uname -a Linux PS001 4.8.0-34-generic #36-Ubuntu SMP Wed Dec 21 17:24:18 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux ProblemType: Bug DistroRelease: Ubuntu 16.10 Package: software-properties-gtk 0.96.24.7 ProcVersionSignature: Ubuntu 4.8.0-34.36-generic 4.8.11 Uname: Linux 4.8.0-34-generic x86_64 NonfreeKernelModules: wl ApportVersion: 2.20.3-0ubuntu8.2 Architecture: amd64 CurrentDesktop: GNOME Date: Sat Jan 28 23:14:17 2017 InstallationDate: Installed on 2017-01-24 (4 days ago) InstallationMedia: Ubuntu-GNOME 16.10.0 2017.01.23 amd64 "Custom Yakkety Yak" PackageArchitecture: all ProcEnviron: TERM=xterm-256color PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_US.UTF-8 SHELL=/bin/bash SourcePackage: software-properties UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/software-properties/+bug/1660100/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp