The COM Add-in (Component Object Model) toolbar button is not on any toolbars by default. You have to add it and then click on it to get to the COM Add-in dialog. First, right click in a blank area around the toolbars and choose Customize
Go to Tools on the left and COM Addins on the right
Drag it onto an existing toolbar – the I bar tells you where it’s going to go
Now it’s on the toolbar, so click it
And you get this dialog. It shows that I have one COM Add-in that it’s not loaded (unchecked).