April 2018
Phone: Xiaomi 5s
OS version: MIUI 9.8.4.19
Connection : Both WI-FI and mobile internet
It started around beginning of April 2018 but after clearing cache and force stop application i could log in into game.
Today 04/25/2018 I'm not able to do it even after "killing" and clearing application. It loading game then asking to connect with google account, I'm choosing account , then it failed due to connection.
June 2018
I'm having the same problem, also using a Xiaomi, have you found any way to solve it?