@pushbullet Well, last night I finally got it working again, so ¯_(ツ)_/¯! If I hadn't, I would have installed from the Chrome store! Thanks!

@petebristol: The users below are correct: completely disable the options at the shield (ad/tracker blocking) then sign in again. It took a few tries, but I was finally able to complete the install of the extension and get it notifying me again.