One possible reason for this is if you are using a private window and the extension is not allowed to run in private windows.

To check on that:

(A) Open the Add-ons page, either

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons
• type or paste about:addons in the address bar and press Enter/Return

(B) In the left column of the Add-ons page, click Extensions.

(C) Find OneNote Clipper on the right side.

If there is no purple mask icon next to the name:

(D) Click the extension name to open its Details panel, and scroll down to where you find this option and click the bubble for Allow:

Run in Private Windows     (*) Allow  (_) Don’t Allow

Was that it?

Thanks for your suggestion. I wasn't using a private window, but that is enabled for OneNote Clipper. Still no icon.

I'll just open Chrome if I need to use the clipper. It works there.

If you go into the Customize mode, is the button available either on the "overflow" list or in the available buttons? Customize Firefox controls, buttons and toolbars

Hi again--

I knew I had to be able to add icons to the taskbar at the top, but didn't know where to do it.

Thanks for the tip about customizing. I've added the clipper and also some things to the overflow area.

Cheers!

Tom