If you've already created an account binding on your account using one of the available login options, you can access your lost data simply by logging in using that account binding. Here's how!
1) Uninstall the app.
2) Reinstall the app. (This will allow you to access the login screen again.)
3) Choose the RETURNING PLAYER button.
4) Choose the Login option you used when you made your account
5) Enter your Login information.
After this, your data will be restored!
If you are still having trouble logging back into your account, could you show us a screenshot of any error messages you are getting and then we can help you out further?