(Solving) Annotate PRO is Hidden
The Annotate PRO icon should always be available at the top right of your browser (just below where the options to minimize or close the browser are (on Windows). If you can’t see it, it might have accidentally been hidden. It’s easy to fix.
In order to make the extension visible again, click on the puzzle piece icon. Next to each extension there is an icon that looks like a thumbtack. If it is grey the extension is hidden from your browser bar. If it is blue, it will be visible. Click on it to change it from gray to blue and Annotate PRO will show up again.
Pro tip: Regardless if AP is visible or not you can open the extension window by pressing Alt + A