I would like to see my Google Calendar in Thunderbird. I am trying to follow the instructions here, but they just don't work. https://support.mozilla.org/en-US/kb/using-lightning-google-calendar Specifically, at Step 4 of "Installing and configuring the add-on" nothing happens. I never get an "Install Now" button. It is as if Thunderbird is just ignoring my instruction to install the add-on. The instructions are extremely simple. I don't think I'm doing anything wrong. So, what's the problem? All advice is appreciated.