The KDE "start button", (K Button) usually found at the Left of the Panel, can cease to function (will not pop up the menu) if you: 1) accidentally drag some arbitrary distance while clicking the menu button, or 2) switch desktops with the menu open. Occurs with the menu alternatives: Application Menu, Application Launcher How to reproduce: (easiest way) Select either App-menu or App-launcher menu alternative. Click K button (start button) menu appears Switch desktop via pager (while menu still showing) Click K button again, and menu will no longer show, but K button becomes underlined briefly How to restore Menu functionality: Any of these methods will restore Menu functionality to the K button 1) Right click the K-button and choose a different Menu Alternative. 2) killall plasmashell && plasmashell (in krunner or a shell) 3) Logout. Found using Manjaro Stable packages KDE Plasma Version 5.12.5 KDE Frameworks Version 5.46.0 QT Version 5.10.1 Kernel 4.14.44-1 (Manjaro) x86-64. Can not reproduce with OpenSuse Leap 15 KDE Plasma Version 5.12.5 KDE Frameworks Version 5.45.0 <------<<< ? QT Version 5.9.4 Kernel 4.12.14-4 (Opensus Leap 15) x86-64.
Same issue with Fedora rawhide (plasma-5.12.90 qt5.11 frameworks 5.46). Kickoff crashes when click on categories. Message from journalctl: file:///usr/share/plasma/plasmoids/org.kde.plasma.kickoff/contents/ui/KickoffItem.qml:211:19: Unable to assign [undefined] to QString Other stuff seems ok (favorites,history ..) I ll try a build from plasma-desktop git.
Rebuilding plasma-desktop from git solves the issue.
Same issue on Archlinux. KDE Plasma 5.12.5 KDE Frameworks 5.46.0 Qt 5.11.0 Kernel : 4.16.12-1-ARCH x86_64 I also had the same bug happen for widgets in the system tray area : none of them could pop up menus, however the application laucher was still working fine. Cannot repreoduce this version of the bug, though.
Seems to be fixed with : KDE Plasma 5.12.5 KDE Frameworks 5.47.0 Qt 5.11.0 Kernel : 4.16.13-2-ARCH
*** This bug has been marked as a duplicate of bug 381242 ***