Here is a guide on how to fix "Account doesn't exist":
After the last update we have made a lot security improvements so in order to deal with all kind of cheats in game we added an advanced anti-cheat system that makes your account doesn't exist If The Anti-Cheat Doesn't Load ! So you need a program called "Visual C++ Redistributable Runtimes"
The Link below can download "Visual C++ Redistributable Runtimes"