Each sign-in method is its own account. If you first signed up with Apple and chose Hide My Email, signing back in with Google — or with the email address you normally use — won't find that account, and the app will start setting up a new one instead.
Go back and sign in the same way you did when you first joined. If you're not sure which method you used, try each one before creating anything new. As soon as you pick the right one, your account, friends and chats come back exactly as you left them.
If the method you originally used isn't offered on your current phone, see "I changed phones and my original sign-in option isn't there".