Pocket Plant not connecting to Fitbit

I bought a fitbit flex 2 because I wanted to use it with this app. I can’t get the app to authorize fitbit at all, like it will not connect. I have tried uninstalling, clearing the cashe, and reinstalling, but that did not help either. My phone is a galaxy note 4 duos. I am not sure why this is not working but any help would be appreciated.