I've developped a custom Extension with SPFX. This custom extension performs a Search. I deployed it. Everything worked totally fine during 6 months. And now, out of the blue, my extension is only visible in Site Content, no more in all the other pages.

What i have :

Custom extension created following the documentation. gulp bundle --ship generated temp files that I uploaded to a folder in a Library called CDN (which has been activated and recorded as a CDN origin). gulp package-solution --ship generated my .appkg that i've uploaded to the appCatalog.

The prompting errors :

Normally, as in my Site Content, in the dev Console, in the Network tab, I find my postquery, with all my query sent to SP. Now, in my pages, when I check the dev console,

  1. in the Network tab, my postquery is not appearing.
  2. In the console tab, I have the following error : "Uncaught (in promise) Error : Failed to create application customizer 'ClientSideExtension.ApplicationCustomizer.XXXXXXXX'.Error information is '***Extension failed to initialize for componentId "XXX".' "

What i tried :

I tried a gulp serve --nobrowser to see if I had any issues. I have none, and my Extension is well displayed.

So, is it a CDN issue ? -even if I don't think so, because the extension works on _layouts pages. Is it another issue ? How to debug that ?

Please help me, I am really stuck there.

Thanks a lot ! :)

  • 1
    Maybe it can relate to update of React in SharePoint Online CDNs. Try to update your local React to the same version and then run gulp serve again to see if the issue occurs. developer.microsoft.com/en-us/sharepoint/blogs/… Dec 27, 2018 at 12:08
  • 1
    Thanks @LukasNespor, But it "just" was Microsoft's update on the SharePoint DOM. I don't remember the details but it was a fregging class modification. My code was an injection of div elements through an extension, and to be injected, it was based on MS's class.. and it changed
    – Gaelle
    Feb 6, 2019 at 16:00
  • hi @Gaelle how did you resolve this? im getting this same exact error where it only loads in the site contents or anywhere else just. not in the site pages
    – Page F.P.T
    Dec 16, 2021 at 8:47
  • 1
    hi @PageF.P.T, sorry for the delay, I hope you found the solution, which was : modify the injection of the extension. It was based on a div class (because there was no div ID), and MS changed this class and the DOM structure. So change yours accordingly :)
    – Gaelle
    May 18, 2022 at 8:26

1 Answer 1


Check which master page is applied to the site /_layouts/15/ChangeSiteMasterPage.aspx. There are 2 master pages as in Site Master Page and System Master Page. In your case System Master Page may be seattle, hence extension is working there.

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