Please provide output of qdbus org.kde.KWin /KWin supportInformation

If you're on X11, you have to move the pointer in order to /trigger/ this effect.

# qdbus org.kde.KWin /KWin
Service 'org.kde.KWin' does not exist.
# qdbus 
:1.1
org.freedesktop.DBus

And moving the mouse has no effect (mouse pointer remains as is).

Is KWin running?

Sorry, KWin was not running. '/usr/bin/kwin_x11' is now running. But no change. 

###
> qdbus org.kde.KWin /KWin
method Q_NOREPLY void org.kde.KWin.cascadeDesktop()
method int org.kde.KWin.currentDesktop()
method QVariantMap org.kde.KWin.getWindowInfo(QString)
method Q_NOREPLY void org.kde.KWin.killWindow()
method void org.kde.KWin.nextDesktop()
method void org.kde.KWin.previousDesktop()
method QVariantMap org.kde.KWin.queryWindowInfo()
method Q_NOREPLY void org.kde.KWin.reconfigure()
signal void org.kde.KWin.reloadConfig()
method bool org.kde.KWin.setCurrentDesktop(int desktop)
method void org.kde.KWin.showDebugConsole()
method bool org.kde.KWin.startActivity(QString)
method bool org.kde.KWin.stopActivity(QString)
method QString org.kde.KWin.supportInformation()
method Q_NOREPLY void org.kde.KWin.unclutterDesktop()
method QDBusVariant org.freedesktop.DBus.Properties.Get(QString interface_name, QString propert
method QVariantMap org.freedesktop.DBus.Properties.GetAll(QString interface_name)
signal void org.freedesktop.DBus.Properties.PropertiesChanged(QString interface_name, QVariantMingList invalidated_properties)
method void org.freedesktop.DBus.Properties.Set(QString interface_name, QString property_name, 
method QString org.freedesktop.DBus.Introspectable.Introspect()
method QString org.freedesktop.DBus.Peer.GetMachineId()
method void org.freedesktop.DBus.Peer.Ping()
###

Is this effect working for both of you?
If so, I would try a fresh install of a KDE/Plasma distro. What is the preferred distro of KDE developers?
Thanks.

> qdbus org.kde.KWin /KWin supportInformation
KWin Support Information:
The following information should be used when requesting support on e.g. https://forum.kde.org.
It provides information about the currently running instance, which options are used,
what OpenGL driver and which effects are running.
Please post the information provided underneath this introductory text to a paste bin service
like https://paste.kde.org instead of pasting into support threads.

==========================

Version
=======
KWin version: 5.16.0
Qt Version: 5.12.3
Qt compile version: 5.12.3
XCB compile version: 1.13

Operation Mode: X11 only

Build Options
=============
KWIN_BUILD_DECORATIONS: yes
KWIN_BUILD_TABBOX: yes
KWIN_BUILD_ACTIVITIES: yes
HAVE_DRM: yes
HAVE_GBM: yes
HAVE_EGL_STREAMS: yes
HAVE_X11_XCB: yes
HAVE_EPOXY_GLX: yes
HAVE_WAYLAND_EGL: yes

X11
===
Vendor: The X.Org Foundation
Vendor Release: 12005000
Protocol Version/Revision: 11/0
SHAPE: yes; Version: 0x11
RANDR: yes; Version: 0x14
DAMAGE: yes; Version: 0x11
Composite: yes; Version: 0x4
RENDER: yes; Version: 0xb
XFIXES: yes; Version: 0x50
SYNC: yes; Version: 0x31
GLX: yes; Version: 0x0

Decoration
==========
Plugin: org.kde.breeze
Theme: 
Blur: 0
onAllDesktopsAvailable: true
alphaChannelSupported: false
closeOnDoubleClickOnMenu: false
decorationButtonsLeft: 0, 2
decorationButtonsRight: 6, 3, 4, 5
borderSize: 3
gridUnit: 10
font: Oxygen-Sans,10,-1,5,50,0,0,0,0,0
smallSpacing: 2
largeSpacing: 10

Platform
==========
Name: KWin::X11StandalonePlatform

Options
=======
focusPolicy: 0
nextFocusPrefersMouse: false
clickRaise: true
autoRaise: false
autoRaiseInterval: 0
delayFocusInterval: 0
shadeHover: false
shadeHoverInterval: 250
separateScreenFocus: false
placement: 4
focusPolicyIsReasonable: true
borderSnapZone: 10
windowSnapZone: 10
centerSnapZone: 0
snapOnlyWhenOverlapping: false
rollOverDesktops: true
focusStealingPreventionLevel: 1
legacyFullscreenSupport: false
operationTitlebarDblClick: 5000
operationMaxButtonLeftClick: 5000
operationMaxButtonMiddleClick: 5015
operationMaxButtonRightClick: 5014
commandActiveTitlebar1: 0
commandActiveTitlebar2: 30
commandActiveTitlebar3: 2
commandInactiveTitlebar1: 4
commandInactiveTitlebar2: 30
commandInactiveTitlebar3: 2
commandWindow1: 7
commandWindow2: 8
commandWindow3: 8
commandWindowWheel: 31
commandAll1: 10
commandAll2: 3
commandAll3: 14
keyCmdAllModKey: 16777251
showGeometryTip: false
condensedTitle: false
electricBorderMaximize: true
electricBorderTiling: false
electricBorderCornerRatio: 0.25
borderlessMaximizedWindows: false
killPingTimeout: 5000
hideUtilityWindowsForInactive: true
inactiveTabsSkipTaskbar: false
autogroupSimilarWindows: false
autogroupInForeground: true
compositingMode: 1
useCompositing: false
compositingInitialized: false
hiddenPreviews: 1
glSmoothScale: 2
xrenderSmoothScale: false
maxFpsInterval: 16666666
refreshRate: 0
vBlankTime: 6000000
glStrictBinding: true
glStrictBindingFollowsDriver: true
glCoreProfile: false
glPreferBufferSwap: 97
glPlatformInterface: 1
windowsBlockCompositing: true

Screen Edges
============
desktopSwitching: false
desktopSwitchingMovingClients: false
cursorPushBackDistance: 1x1
timeThreshold: 150
reActivateThreshold: 350
actionTopLeft: 0
actionTop: 0
actionTopRight: 0
actionRight: 0
actionBottomRight: 0
actionBottom: 0
actionBottomLeft: 0
actionLeft: 0

Screens
=======
Multi-Head: no
Active screen follows mouse:  no
Number of Screens: 2

Screen 0:
---------
Name: HDMI-1
Geometry: 0,0,1920x1200
Scale: 1
Refresh Rate: 60.0197

Screen 1:
---------
Name: DVI-I-1
Geometry: 1920,0,1024x1280
Scale: 1
Refresh Rate: 59.9502


Compositing
===========
Compositing is not active

> Compositing is not active
You need to enable compositing.

(In reply to Vlad Zagorodniy from comment #8)
> > Compositing is not active
> You need to enable compositing.

Thanks a lot, Vlad: It's working now!
Sorry for the noise...