Custom Icon selected but not showing in editor or page

I created a TikTok icon using the methods suggested in documentation, uploaded the zip file to the custom icons section, selected the icon and included necessary information. However, the icon is not showing up when added. See screenshots: the icon SHOULD be appearing where the red arrow is, but it's not showing up at all.

Screenshot 1: shows the icon in the custom icon library.
Screenshot 2: shows the information for the tiktok icon with link - it was previously saved so the save button is greyed out; the icon should appear where the red arrow points. It's not.

What step am I missing?

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