I just clicked "Forgot password" in the scannable app (appears after a failed sign in), then followed the password reset steps via e-mail to reset the password on my account. This appears to have converted my account to an actual evernote account, using the gmail account from my google account that I originally used to sign in with. Once you choose a new password and complete the password reset, you should be able to login with that email and new password in Scannable.
Hope this helps!