If you are getting a message that says there is no password set up on your account, this means that you signed in through Facebook and do not have a password set up on your account. If you want to disconnect your Facebook, you will need to set up a password on the account. To do this, go to your account Settings.
Be sure you are on the General Page
Click Change Password at the bottom of the page:
You can set up a new password on your account here. You will then be able to disconnect your Facebook profile from your Sonlet account.