Please attach a screenshot that shows the problem.

Are they clickable even though their icons are missing? Or are they not clickable either?

So. I have a taskbar:
left: application menu, some shortcuts. Center: my app icons (icon only taskbar), right: system tray, some miniprograms

now it happens that I launch applications and their icon does not show up in the icon-only taskbar. They appear when pressing "Alt+Tab" but I cant click on them in the taskbar. This is the weird part.

Sometimes after a while the icons appear, mostly they dont at all.

hard to make a screenshot of that haha, but I will try to get some logs.

ok some new info: this is happening on X11 too:
- freetube flatpak
- VLC (no tray icon) flatpak

They are randomly not showing up. Now Freetube is showing up normally again, VLC is not (I open a video and it opens as foreground window, no icon in tray shown)

@Nate Graham there is no icon, no Wayland/X11 Placeholder and no empty space. My taskbar is centered to I always see if there is an empty space.

VLC shows the regular icon in the Alt+Tab view, Freetube has an icon in tray but shows the generic X11 icon in the alt tab switcher. This is all quite random.

it seems that icons appear like 5min after the app runs, sometimes. The VLC icon appeared normally now, after a while.

Maybe this journalctl log helps?

Aug 21 13:27:51 ThinkPadT495 flatpak[2198]: [13:27:51.285] [DBG] PwPipelineManager::on_destroy_node_proxy: Stream/Output/Audio 63 ALSA plug-in [vlc.bin] has been removed
Aug 21 13:27:51 ThinkPadT495 systemd[1415]: app-flatpak-org.videolan.VLC-37983.scope: Consumed 3.164s CPU time.
Aug 21 13:27:52 ThinkPadT495 flatpak[2198]: [13:27:52.235] [DBG] FilterContainer::on_link_changed::<lambda>: No app linked to our device wants to play. Unlinking our filters.
Aug 21 13:27:52 ThinkPadT495 flatpak[2198]: [13:27:52.235] [DBG] FilterContainer::disconnect_filters: disconnecting the JamesDsp filter from PipeWire
Aug 21 13:27:57 ThinkPadT495 avahi-daemon[1047]: Registering new address record for fd57:2b00:3948:436f:2721:b345:f09e:5b44 on wlp1s0.*.
Aug 21 13:28:03 ThinkPadT495 avahi-daemon[1047]: Withdrawing address record for fd57:2b00:3948:436f:2721:b345:f09e:5b44 on wlp1s0.
Aug 21 13:28:19 ThinkPadT495 kstart5[38122]: Omitting both --window and --windowclass arguments is not recommended

interestingly when scrolling the taskbar the window appears, as well as when showing the alt+tab view

edit: this is also not happenig for virt-manager, two windows open, on X11, installed as RPM

Are only Flatpak apps affected? Can you do some troubleshooting and see if it happens with all Flatpak apps, some Flatpak apps, or a mixed set of Flatpak apps and distro-packaged apps?

Also, screenshots if the issue would still be helpful.

sorry for not responding quicker. No, not only Flatpak apps, all Apps, Qt, KDE, RPMs, Flatpaks, GTK, doesnt matter

I have this happen with Konsole, Libreoffice, Freetube and more. I am on Fedora Kinoite so all RPMs are distro prepackaged

https://cloudsync.uol.de/s/cFk2dEdEB5deqPq
https://cloudsync.uol.de/s/zAkRtHqfJxmwdtS

virt-manager RPM
https://cloudsync.uol.de/s/zDbFBRWD8rbwE52

XNView is a Flatpak from Flathub

interesting, it seems I cant reproduce this once the apps were already loaded. Also for new apps I can now not reproduce it again. 

Like, Libreoffice writer was not showing up, now its showing always. But now, after three programs not showing up in a row, I cant reproduce this anymore.

Seems to happen on the start of a new session? I am logged in four hours now though. Maybe app icon cache? But as I said there are no empty boxes too, not only the icons are missing.

This is very confusing. :/

Any chance you could take a screen recording that shows you reproducing the bug?

duplicate of 396616?

I will try same machine, vanilla user profile.

The video wont show anything.

Something interesting: When I launch an app and KDE shows the "loading animation" (which is actually broken when you turn animations to instantly, another bug I will file) in the application bar, it will show.

But sometimes I launch an app and suddenly there pops up the icon, without the loading. During this process, whatever it may be, the popup of the icon could fail.

(In reply to Fushan Wen from comment #13)
> duplicate of 396616?

I dont think so as I dont ever have multirow enabled, I dont find the setting but I am sure its disabled

Ah right, it probably is Bug 396616.

In the Task Manager settings window, set "maximum rows" to 1. Does that fix the issue? If so, it's Bug 396616.

I already set the rows like that.

New thing: when enabling animations many "disappearing things" in Plasma seem to work. I normally disable Animations by setting the speed to instant. I think having an option for that is really important for low end hardware and speed. But I like the fluidity and it seems to fix a lot of issues... weird

so to make it clear, I already went to the taskbar settings in the past and set the rows to 1, so not that bug

Is this still reproducible at all in a recent version of Plasma 6, like 6.1.4 or later?

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This is fixed without a doubt. Thanks for your work!