Have recently faced the same issue on Ubuntu 18.04. It occurs rather frequently, sometimes, within ten minutes. Previously, it has never occurred. Same message is printed in the logs.
Upgrade to Ubuntu 20.04, which ships GNOME Shell 3.36.2, did not help. There is an immediate workaround, documented on the unix stack exchange/ Switching to login screen (Ctrl+Alt+F1) and back to the main (Ctrl+Alt+F2) helps: https://unix.stackexchange.com/questions/502315 /gnome-partially-stops-responding-to-mouse-keyboard -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to gnome-shell in Ubuntu. https://bugs.launchpad.net/bugs/1734095 Title: Software & Updates not showing authorization popup [gnome-shell[N]: pushModal: invocation of begin_modal failed] Status in GNOME Shell: Confirmed Status in gnome-shell package in Ubuntu: Confirmed Bug description: After upgrading to Ubuntu 17.10 (from 17.04), if I open the Software and Updates app and attempt to change anything it does not popup the authorization dialog and will not let changes through. In sylog I see Nov 23 10:07:04 tigger gnome-shell[2142]: polkitAuthenticationAgent: Received 3 identities that can be used for authentication. Only considering one. Nov 23 10:07:04 tigger gnome-shell[2142]: pushModal: invocation of begin_modal failed Nov 23 10:07:04 tigger gnome-shell[2142]: polkitAuthenticationAgent: Failed to show modal dialog. Dismissing authentication request for action-id com.ubuntu.softwareproperties.applychanges cookie 1-28e9d285258e7cd70c2af2980886a55b-1-cff4894642cc4a6c033597370ee1f740 Nov 23 10:07:04 tigger software-properties-gnome.desktop[3367]: ERROR:root:Authentication canceled, changes have not been saved Before the upgrade it was ok. Other apps that require authorisation function as expected. ProblemType: Bug DistroRelease: Ubuntu 17.10 Package: gnome-shell 3.26.1-0ubuntu5 ProcVersionSignature: Ubuntu 4.13.0-17.20-generic 4.13.8 Uname: Linux 4.13.0-17-generic x86_64 ApportVersion: 2.20.7-0ubuntu3.5 Architecture: amd64 CurrentDesktop: GNOME Date: Thu Nov 23 10:07:44 2017 DisplayManager: lightdm InstallationDate: Installed on 2014-10-21 (1128 days ago) InstallationMedia: Ubuntu 14.10 "Utopic Unicorn" - Alpha amd64 (20141017) SourcePackage: gnome-shell UpgradeStatus: Upgraded to artful on 2017-11-22 (0 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/gnome-shell-legacy-bugs/+bug/1734095/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
