Update Notifier "Restart" action does not trigger system reboot.

[cmd_er]

After installing updates, the Update Notifier shows the “Restart required” prompt. However, clicking the Restart button provided by Update Notifier does not trigger any reboot sequence. The button simply does nothing—no shutdown signal, no logout, and no transition into reboot.

Regular system reboot via the system menu or using the reboot command works normally.
The issue occurs only when attempting to reboot through the Update Notifier’s post-update restart button.

ProblemType: Bug
DistroRelease: Ubuntu 25.10
Package: update-notifier 3.201
ProcVersionSignature: Ubuntu 6.17.0-7.7-generic 6.17.2
Uname: Linux 6.17.0-7-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.33.1-0ubuntu3
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Fri Nov 28 03:31:42 2025
InstallationDate: Installed on 2025-10-09 (49 days ago)
InstallationMedia: Ubuntu 25.10 "Questing Quokka" - Release amd64 (20251007)
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
SourcePackage: update-notifier
UpgradeStatus: No upgrade log present (probably fresh install)