Thats What Not Your Wiki States:
After the game loads, the login screen will appear. It includes a large Pony Vs Pony logo, its game version, two fill-in boxes where you can enter your Username and Password, a large "Login!" button which brings you to the next screen after your sign in info is filled, a "Register!" button which links to either a page where you can make an Artix account if you don't have one or your Artix Entertainment Master Account screen if you're already signed in on Artix's website, a "Forgot Your Password?" button, in simple font, which links you to an Artix page of what to do when you've lost your Artix account password; and two save buttons, one next to each fill-in box, which will save what's written on that box next time you visit the game. When you put your cursor over the words "Username" and "Password", a pop-up message will appear for each of them.
If you sign in with your username or password spelled wrong, you'll enter an error screen with a "Reset!" button. Clicking it will take you back to the login screen. Any other error messages in the game will also bring you back to the login screen.
PVP always required your Artix Account
Not sure how still playable for you PVP no longer loads up on my end