i was getting a lot of the same error code 400 for the past 3-4hrs. i decided to finally contact support (customer service button when you login, to the top right there’s a chat button), wrote what was happening but didn’t get a response, loaded back into the game, got an error for a payment system this time (haven’t actually paid or used any payment systems) and then boom, when i logged in again it was working fine...... so while i have no idea whether it’s working fine because they fixed the server just in that time period or if it was a google account issue or just talking to the support helped, if you’re still having that issue, maybe give those steps a try?