During the update on August 7th 2015, there was changes to the account and login systems. An email will be sent with instructions on how to reset your password.
Due to this change your old password will no longer work, therefore you will need to download the new version of the sync tool listed here.
Once you have installed the new version, you will need to use your API key instead of your password to login. Information on how to retrieve your API key can be found here.