Hello, I was informed that the Google+ login method was removed from the miniclient. However, there is a method to bypass the Google+ login, binding an email to your account. You can do this through your User Center, which can be found in the link provided below. If you do not see an option to bind your email, you c*so set a security email and use that to login.

https://naruto.oasgames.com/en/serverlist

If it is stating that you already have the email account in use, that means that the email you are using is registering as an account already. If you are unable to use this email address, then I suggest adding a security email to your account, as this will allow you to login using that email address as well. If you have access to your user center, through the link I sent above, you can add security methods there.