Firefox watcher not logging data

Hello, I installed Activity Watcher today on Ubuntu 18.04 with Firefox 66.0.3. Thank you very much for making this software.

I added the firefox web watcher a few hours ago, but there is no data in the aw-watcher-web-firefox bucket. aw-watcher-window bucket is logging Firefox window titles fine. Might the problem be that I clear firefox Data (including cache) and History daily?