I'm trying to debug a Gnome Shell extension called multi-monitor addon. I'm running PopOS. I was using the multi-monitor addon just fine for quite some time, and yesterday I rebooted and the extension became disabled.

When I open the Gnome Extensions in the browser (https://extensions.gnome.org/extension/921/multi-monitors-add-on/) it shows as disabled. When I enable it nothing happens and when I refresh the page it remains disabled.

I tried following this stack exchange article to get logs using journalctl, but I didn't see any logs that were more recent than 3 weeks old.

I really don't know what I'm doing with Gnome shell extensions, they're totally new to me (I am new to PopOS and more familiar with Linux Mint which never used Gnome Shell extensions).

I could use some direction on how to go about tracking down an error message that will help me understand what's broken.


I've noticed in journalctl logs the following error repeating itself:

Dec 17 10:31:49 popsicle gnome-shell[2834]: JS ERROR: TypeError: null has no properties

In the Extensions UI control panel I see the Multi Monitor Add-On, but I cannot enable it. It simply ignores attempts to click on the enable/disable slider. This is the same behavior I get in the Gnome Extensions Firefox addon website when I try to enable it there as well. I've also removed it and added the extension again with no change in behavior.

  • What does "GNOME extensions" app say?
    – mattia.b89
    Jan 16 at 15:08
  • It's a Firefox browser addon (addons.mozilla.org/en-US/firefox/addon/gnome-shell-integration/…). It loads a web page and handles installation of the gnome extensions. I don't know how to investigate these shell extensions, that's what I need to understand in this question. Jan 16 at 21:25
  • 1
    $ gnome-extensions-app
    – mattia.b89
    Jan 16 at 21:47
  • Ah, that's the settings panel. The multi monitor add-on exists there, but I cannot enable it. I did notice that logs exist in journalctl that might be related, I've updated the question with what I see. Jan 16 at 21:52
  • Ah, dumb answer: all extensions were disabled. In the top right of the gnome-extensions-app there's a slider to disable extensions (which only had the effect of disabling the one manually added extension). @mattia.b89, if you would simply post as an answer to look in gnome-extensions-app and verify that extensions are enabled I'll happily accept the answer, you pointed me to the UI I needed to look in. I was focused on the shell extensions firefox plugin where I installed it, which gave no indication of what I should look at. Jan 16 at 22:03

Starting with version 3.36 [1], GNOME provides a simply tool to manage extensions, simply called Extensions: you can launch it via gnome-shell or terminal

$ gnome-extensions-app

It is a useful tool because you can control extensions and especially inspect potential issue since it gives you information about errors (a feature that most-known gnome-tweaks-tool does not provide).

So, please take an easy look there.

[1] https://www.phoronix.com/scan.php?page=news_item&px=GNOME-Shell-Extensions-App

  • I repeated the problem. It turns out that when PopOS reboots after a failure it disables all extensions, obviously to avoid boot problems potentially caused by extensions. It was this automated disabling of extensions that caught me unaware. The gnome-extensions-app is installed in PopOS by default. It can be opened by searching "Extensions" in the app search bar. Jan 17 at 18:28

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