[Solved]

FYI: I should add that I was using the Swiftkey Tablet X keyboard app, and not the standard Android keyboard. When I tried to change the keyboard to the standard Android one, and reran your app, it started showing the "login" button again. I then tried to reproduce the bug by alternating between the keyboards and force stopping the app in between. No success in reproducing the bug. Maybe it was related to me switching keyboards, or maybe the bug just happened to resolve itself for another unknown reason, at just the same time I tried to switch keyboard.