Help! I feel incredibly stupid but I cannot figure out how to annotate articles. I've opened the article in Zotero and can see the buttons for annotations, but they are greyed out and do not work to highlight the text.
https://s3.amazonaws.com/zotero.org/images/forums/u1010570/x8dj4cub614774u0lv19.jpg

I have updated Zotero and looked through the settings, but I can't figure it out.

Thanks in advance for the help!