Possible work-around for Android users experiencing log in issues (recreated on two different devices running 4.4.2):
1. Enable syncing (can be quickly enabled via sync icon from the Android swipe down menu).
2. Open Google Play Games app
3. Swipe from the left to open Play Games' menu and select 'My Games' (might have to select 'All My Games' on next screen).
4. Select Pathfinder Adventures and then launch the app from the red play button on the right side.
5. You should now be able to log in! (You may have to accept a sync request from the swipe down menu or tap the 'Link Social Gaming Network' button for it to work)
Hopefully this helps some people.
(I've seen a bunch of posts suggesting to open the game via Play Games before, but it didn't work for me until I turned on Syncing)
