Extension icons don't appear

Description of the issue:
When I install any extension, the extension’s icon appears briefly in the top right where I expect it to, but then disappears; I can’t pin it or interact with it.

When I open the Extensions manager page, the extension is there and listed as installed/enabled, but there’s no option to display or pin it there, either. Since I can’t get at the icon, I can’t use the extension.

Steps to Reproduce
This happens with any and every new extension.

  1. Go to Chrome web store
  2. Find an extension I want
  3. Click ‘Add to Brave’
  4. Message box appears at top right saying the extension has been added
    At this point, the extension’s icon appears in the toolbar at top right until the message box is dismissed, at which point the icon is never seen again.
  5. I yell at Brave browser, demanding that it return the icon so that I can use the freakin’ extension I just downloaded

I do have a few extensions that I installed months ago, which are properly pinned–I just can’t add any more!

Expected result:
I’d really like to be able to add and use new extensions.

Brave Version:
Version 1.21.76 Chromium: 89.0.4389.86 (Official Build) (64-bit)