I used Doodle God as a test game. It downloaded, but very very slowly. Then I got two pop-up Windows notifications saying that all chunks had downloaded and then that the game had installed and was ready. Everything's working great!
I was getting the same "User does not exist" error, but I found a workaround! I noticed that the email address stored in my account is written in all lowercase, but I was typing it with the first two letters capitalized. I know it doesn't really matter in the grand scheme of things, that's how...